Whether you're into scaling mountains, saving the rain forest or planning vacations around your furry friends, there's a travel organization, Web site or non-profit out there to help pull off an amazing trip. The listings below are among the best resources for some of the more popular specialty travel topics. One umbrella organization, the aptly named Specialty Travel Index (888-624-4030, www.specialtytravel.com), publishes a biannual magazine covering everything from gorilla viewing to barge tours.

Adventure Travel

* Appalachian Mountain Club, 800- 411-5776, www.outdoors.org. Hike through the northeast (mainly New England) with the oldest recreation group in the United States. Excellent workshops and family outing suggestions on its Web site.

* Away.com, www.away.com. Extensive site that features Top 10 lists of places, activities and adventures, and highlights travel deals. Also, great photography (including a "Behind the Image" section) and feature stories. The same company owns GORP Travel (877-440-4677, www.gorptravel.com), a guide and reservation service that also includes destination reviews and "best of" lists.

* iExplore.com, 800-439-7567, www.iexplore.com. National Geographic invested in this adventure and experiential travel agency that offers trips around the world, from Mount Kilimanjaro to Costa Rica's Monteverde Cloud Forest.

* National Outdoors Leadership School, 800-710-6657, www.nols.edu. Pricey wilderness trips that make going back to school an adventure -- great for working on those mountaineering and backcountry survival skills. Undergrads at more than 400 colleges can receive college credit for semester courses.

* Sierra Club, 415-977-5522, www.sierraclub.org/outings. The environmental group offers more than 350 volunteer-led trips worldwide, including 90 volunteer vacations in the United States, Canada and Puerto Rico.

* Trails.com, www.trails.com. Descriptions and maps of 30,000 trails can be accessed for free at this all-trails-all-the-time site. The new Topo Finder lets the cartography-crazed search for topographical maps anywhere in the United States. Annual membership for full benefits starts at $29.95.

* Wilderness Travel, 800-368-2794, www.wildernesstravel.com. Offers intense, expert-led -- and expensive -- cultural, trekking, archaeological and oceanic expeditions worldwide. New this year: Libya.

Eco-Travel

* Audubon Naturalist Society, 301-652-9188, Ext. 11, www.audubonnaturalist.org. The local preservation group's Travel Program offers trips to observe the outdoor world.

* Better World Club, 866-304-7540, www.betterworldclub.com. Organization that touts itself as more socially responsible than AAA, offering roadside assistance and eco-friendly car rental discounts. Its travel service charges $35 for inquiries. Basic membership is $53.95 a year.

* Conservation International's Ecotravel Center, 800-406-2306, www.ecotour.org. The center doesn't offer vacation ideas or itineraries, but its Web site does have profiles of biodiversity spots and provides information on in-country eco-friendly agencies.

* Green Hotels Association, 713- 789-8889, www.greenhotels.com. The folks who ask if you really need a new towel every day offer a Web site with eco-conscious hotels arranged by state.

* International Ecotourism Society, 202-347-9203, Ext. 275, www.ecotourism.org. Organization members can answer eco-tourism questions, or become a member for $35 and use the Web site to find tour operators, eco-friendly lodging and specialized info by region.

* National Audubon Society, 800- 967-7425, www.audubon.org. The worldwide, natural-history-focused "Nature Odysseys" work with companies that adhere to the society's eco-sensitive travel ethics.

* National Park Service, 888-467-2757 www.nps.gov. An all-inclusive site for anything and everything to do with traveling to national parks. Links to www.recreation.gov, with information on wildlife watching, hunting/fishing permits; also links to the National Registry of Historic Places site's "Discover Our Shared Heritage Travel Itinerary Series." Offers the Golden Age Passport, which includes admission to national parks and discounts for those 62 and older; $10 for a lifetime pass (the comparable National Parks Pass is $50 per year for those under 62).

* Nature Conservancy, 888-883-0736, www.nature.org/aboutus/travel. Its "Conservation Journeys" division partners with eco-tour companies in some of the world's "Last Great Places," highlighting a few destinations annually (for 2005 it's partnered with Emerald Planet for trips to Honduras and the Dominican Republic).

* Planeta.com, www.planeta.com. Eco-travel clearinghouse with a Latin American focus. Limited trip-planning resources, but the site offers a travel forum, book reviews and an extensive directory of Spanish language schools.

Educational/Language

* Interhostel, 800-733-9753, www.learn.unh.edu/interhostel. Interhostel's reputable programs are for travelers over 50 (if you want to bringthe kids or grandkids, try the associated Familyhostel program). The University of New Hampshire- sponsored trips mix lectures and excursions.

* Lingua Service Worldwide, 800-394- 5327, www.linguaserviceworldwide.com. The independent agency represents schools for nine languages with intensive, full-immersion programs in 18 countries. Prices are listed in dollars for easy comparisons.

* Shaw Guides, 212-799-6464, www.shawguides.com. A comprehensive source with more than 5,300 listings for cultural, art, photography, language and cooking vacations, with links to more complete info.

* Smithsonian Journeys, 877-338-8687, www.smithsonianjourneys.org. Premier (and expensive) worldwide educational programs organized by the venerable Smithsonian. Members only, but the $29 per household fee can be added to your trip.

* Study Abroad.com, 610-499-9200, www.studyabroad.com. Listings shouldn't be taken as endorsements, but the site is a good resource for undergrads looking for different study-abroad options, with separate categories for non-students and those 55 and older.

Family

* Family-Reunion.com, www.family-reunion.com. "Mister Spiffy" offers hints on good reunion locations, organizational tips, entertainment suggestions and geneology guidelines, all with a sense of humor.

* FamilyFun.com, www.family.com/travel. Disney-produced Web site with many non-Disney vacation ideas, plus travel checklists and tips for those with tweens.

* Family Travel Files, www.thefamilytravelfiles.com. The TravelPhases page of this site reviews age-appropriate destinations; another great item is the list of special events and festivals organized by state.

* Family Travel Forum, 212-665-6124, www.familytravelforum.com. Membership-based online newsletter that lists family-friendly travel agents and tips, with links to its other Web sites, Tiny Travelers and Kid Travels. $38 annual membership.

* Family Travel Network, 703-905-9858, www.familytravelnetwork.com. The site is packed with inexpensive vacation deals, plus tips on warm-weather holiday destinations and links to family-friendly travel agents -- and it's free.

Gay

* Damron, 800-462-6654, www.damron.com. Damron publishes travel and accommodation guides and offers an online database of 15,000 gay-friendly and gay-owned establishments.

* GayRes.com, www.gayres.com. This gay-owned company specializes in discounts for budget and luxury gay-friendly accommodations worldwide.

* GayTravel.com, 800-429-8728, www.gaytravel.com. Gay-friendly vacation booking service, with an active travel forum.

* International Gay and Lesbian Travel Association, 800-448-8550, www.iglta.com. Trade association promoting gay tourism, whose Web site has links to both gay-owned and gay-friendly accommodation booking services, independent B&Bs and travel agencies.

* Out and About, 800-929-2268, www.outandabout.com. The company offers a comprehensive monthly newsletter for gay men and lesbians and publishes travel guides.

* Travel Alternatives Group, 415-437- 3800, www.gaytravelnews.com. Organization that certifies travel agents and tour outlets as gay-friendly.

Health/Disability

* Access-Able Travel, 303-232-2979, www.access-able.com. Comprehensive site of travel agencies, tours, cruises and travel tips for mature travelers and those with special needs.

* Centers for Disease Control and Prevention, 877-394-8747, www.cdc.gov/travel. Indispensable site for travel info on diseases and prevention from the U.S. Department of Health.

* Emerging Horizons, 209-599-9409, www.emerginghorizons.com. Quarterly magazine for people with mobility disorders, including slow walkers. Extensive travel resources include accessibility info for Krakow, for example, a stellar Q&A column and an "Innsiders" column that highlights B&Bs. Annual subscriptions are $14.95. No advertising.

* Global Dialysis, www.globaldialysis.com. Listings of dialysis centers in 115 countries as well as travel agents who specialize in working with dialysis patients. Sign up for the free newsletter for the most up-to-date info.

* International Association for Medical Assistance to Travellers, 716-754-4883, www.iamat.org. Web site lists recent health-related articles on such topics as West Nile and avian influenza outbreaks. Become a member for free and get the worldwide listings of English-speaking doctors with medical training in the United States, Canada or Great Britain who charge a set fee for initial consultations.

* Medical Travel Inc., 800-778-7953, www.medicaltravel.org. Travel agency sets up vacations for dialysis and oxygen patients and families of the terminally ill. Arranges for rental equipment such as golf carts and oxygen tanks.

* MedicAlert, 888-633-4298, www.medicalert.org. Worldwide emergency medical info service. Members wear a special bracelet or necklace engraved with an ID number that is linked to medical history. Membership is $35 for the first year, $20 annual renewal fee.

* Mobility International USA, 541- 343-1284, www.miusa.org. MI's mission is to include the disabled in global exchange programs. The very basic Web site also has links to organizations worldwide.

* Society for Accessible Travel and Hospitality, 212-447-7284, www.sath.org. Advocacy group represents disabled travelers and maintains lists of tour operators. Helpful staff and a well-stocked Web site with a list of disabled-travel organizations. Member- ship ($45 per year) garners discounts with participating travel agents and hotels.

* Travel O2, 888-467-3563, www.travelo2.com. Specializes in info and rentals for travelers who depend on special oxygen supplies.

Pets

* Animal Plant Health Inspection Service, 866-723-4827, www.aphis.usda.gov/travel. The official word from the U.S. Department of Agriculture on what you can and cannot do when traveling with pets.

* Hike With Your Dog.com, www.hikewithyourdog.com. The "Park of the Month" archives detail the doggy life in a particular U.S. park each month (with links), and you can search for dog-friendly hikes by state. Other pages suggest relevant books and give advice on traveling with dogs. Also offers "Hike With Your Dog" tours of the mid-Atlantic region.

* Pet Friendly Travel.com, www.petfriendlytravel.com. Lodging listings in the United States and Canada focus on condos, cabins and private homes that allow pets. Listings provide info on local activities and special pet-friendly amenities.

* Pet Travel Inc., 954-684-9535, www.pettravel.com. Worldwide lodging info with 19,128 listings. Also, comprehensive info on immigration laws, airline policies and pet-friendly restaurants.

* Pets on the Go, 781-934-7202, www.petsonthego.com. Pet-friendly hotels, destination reviews and other resources on the info-packed site. Membership ($15 annually) allows you to customize your search and access premium content.

* Pets Welcome.com, 845-297-5150, www.petswelcome.com. Excellent listings on a variety of pet-friendly lodgings, info on international travel and tips on dealing with emergencies. New this year: "Hurricane Info Exchange" forum. The "Search by Route" feature allows you to see pet-friendly lodging between your starting point and final destination.

Seniors

* AARP, 888-687-2277, www.aarp.org. Popular advocacy group offers great travel discounts among its other services. Membership (50 and older only) is $12.50 a year.

* Elderhostel, 877-426-8056, www.elderhostel.org. Nonprofit group organizes adventures for almost a quarter-million travelers over 55 each year. Take the grandkids on one of the Intergenerational programs, or check out the associated Road Scholar program at www.roadscholar.org.

* Grand Circle Travel, 800-553-1129, www.gct.com. This company markets tours and cruises specifically to the over-50 set (but all ages welcome), and efforts are made to limit single supplements for solo travelers. The tours have a reputation for being unhurried and immersing travelers in local culture. The Overseas Adventure Travel division offers trips a bit bolder than those under the Travel division.

* Hostelling International USA, 202-783- 6161, www.hiusa.org. This site covers low-cost lodging in the United States, with links to hostel information in more than 60 countries available to people of all ages, not just grungy backpackers. Membership for those 55 and over is $18 a year (normally $28 a year) and includes international travel insurance coverage and discounts on Greyhound.

* National Association of Retired Federal Employees, 800-627-3394, www.narfe.org. Group for federal retirees and their families offers travel discounts among its perks. Membership is $25 a year plus local chapter dues if you join before retiring, $33 annually after retirement.

* Senior Summer School, 800-847-2466, www.seniorsummerschool.com. Mostly two- to six-week summer educational programs with classes and lectures in political science, art, etc. The sessions are at 11 universities in the United States and Canada, with Atlanta added as one of this year's seven-day New Year's trips.

Singles

* Connecting: Solo Travel Network, 800-557-1757, www.cstn.org. Helps solo travelers find compatible traveling partners through a bimonthly newsletter and offers tips on single supplements and other downsides of solo travel. Full annual membership is $45 ($28 for Internet-only membership).

* Going Solo Travel Club, 888-446-7656, www.goingsolotravel.com. Offers international tours for single travelers -- married folks are welcome as long as the spouse is left behind -- and matches travelers with roommates to avoid single supplements. No membership fees.

* O Solo Mio Singles Tours, 800-959- 8568, www.osolomio.com. Travel club of group trips for individuals -- no "fuddy duddies" allowed. It aims to arrange roommates for those who want them, but it's not guaranteed.

* Singles Travel International, 877-765- 6874, www.singlestravelintl.com. Agency guarantees you a roommate on its singles-only trips -- or it will pay for the single supplement itself. Also offers single-parent trips where kids are welcome.

* Solo Dining.com, 800-299-1079, www.solodining.com. Tips and strategies for dining alone, with a free online newsletter with advice on tipping and how to avoid getting a bad table.

* Travel Alone and Love It.com, www.travelaloneandloveit.com. This Web-only free newsletter, penned by a flight attendant, has a helpful Q&A page and 10 new solo travel tips posted every month. Also links to numerous helpful Web sites.

* Travel Chums, 212-787-2621, www.travelchums.com. Anonymous, free membership to contact travelers or place ads for travel companions (while other solo travel sites specifically state that they're not a dating service, Travel Chums doesn't rule out the "potential for romance and a long term relationship").

Vegetarian/Dietary

* Green Earth Travel, 888-246-8343, www.vegtravel.com. Vegetarian and eco-specialist local travel agency that also focuses on working with non-profit organizations; a Vegan Alaska trip is planned for 2005.

* Happy Cow's Global Guide to Vegetarian Restaurants, www.happycow.net. Lists cow-free restaurants (six in Reykjavik, for example) and health food stores worldwide. There's also a "vegetarian singles" forum.

* Shamash: The Jewish Network, www.shamash.org/kosher. Searchable database of 1,800 kosher restaurants in 40 countries. The site does not vouch for the accuracy of info, so ask the establishment for its kashrut certification to make sure.

* Vegetarian Resource Group, 410- 366-8343, www.vrg.org. Publishes books on vegetarian travel and links to VegDining.com (www.vegdining.com), which lists veggie restaurants worldwide.

Volunteer Vacations

* American Hiking Society, 800-972- 8608, www.americanhiking.org. One- and two-week trips to preserve U.S. trails while camping. You supply the camping equipment, work six to eight hours daily and help with chores. Trips cost $100.

* Amizade, 888-973-4443, www.amizade.org. Both short- and long-term community service projects in 11 countries in Africa, Asia, Australia, Europe, South America and the United States. Trips range from $530 at Yellowstone to almost $3,000 in Tanzania. Updated Web site will launch in mid- October.

* Cross Cultural Solutions, 800-380- 4777, www.crossculturalsolutions.org. Two- to 12-week humanitarian trips in 10 countries, with the specific task tailored to your skills and interest. Fees ($2,279 to $4,873) include all in-country expenses.

* Earthwatch Institute, 800- 776-0188, www.earthwatch.org. Collect data alongside scientists on archaeological digs and wildlife studies, from the bogs of Belarus to the dolphins of Brazil. All levels of expertise welcome. Trips usually range from one to two weeks, $700-$4,000.

* Earth Island Institute's Global Service Corps, 415-788-3666, Ext. 128, www.globalservicecorps.org. Volunteers participate in educational, health care, sustainable agriculture and HIV/AIDS programs in Thailand and Tanzania. Costs start at about $2,075 for two weeks.

* Explorations in Travel, 802-257- 0152, www.volunteertravel.com. Short-term individual placements with ecological, conservation and wildlife projects in Ecuador, Costa Rica and Puerto Rico. $775-$975 for the placement; volunteers responsible for their expenses.

* Global Volunteers, 800-487-1074, www.globalvolunteers.org. Volunteers work in the United States and abroad (19 countries, including Ghana and the Cook Islands) on projects determined by locals to be most important, such as job skills or health care. Most volunteers for the one- to three-week programs are 50 to 80 years old. Costs $750-$2,900.

* Habitat for Humanity's Global Village Program, 800-422-4828, www.habitat.org/GV. Short-term house-building projects in 80 countries. Costs $1,200-$4,000.

* Health Volunteers Overseas, 202- 296-0928, www.hvousa.org. Health-related teaching programs for seasoned medical professionals -- specialties include physical therapy, pediatrics, nursing, hand surgery and internal medicine -- in more than 25 countries. Average assignment is one month. Volunteers cover their expenses, usually around $2,400.

* International Volunteer Programs Association, 212-807-8686, www.volunteerinternational.org. Links to organizations with volunteer exchange programs that suit your interest or destination.

* Passport in Time, 800-281-9176, www.passportintime.com. Archaeological and historic preservation programs by the U.S. Forest Service. No fee to participate, but you often must provide your own transportation, food and lodging.

* Wilderness Volunteers, 928-556- 0038, www.wildernessvolunteers.org. More than 40 weeklong projects on U.S. public lands (mostly national parks), in which you'll maintain trails, weed and prevent erosion -- and still have free time. Most trips are less than $200 a week. Camping gear is not supplied, and you have to pass a Body Mass Index test.