Honorable mentions: Look to nonprofits that work on environmental issues. Conservation International runs http://www.ecotour.org, which details approved ecotourism destinations in developing countries including Guatemala, Panama and Ghana. Audubon Naturalist Society (http://www.audubonnaturalist.org), the National Audubon Society (http://www.audubon.org) and the Nature Conservancy (http://www.nature.org) offer ecotourism trips.
Frequent fliers. Frequent-flier expert Randy Petersen runs several sites devoted to the topic. Best overall is Web Flyer ( http://www.webflyer.com/), which offers extensive details on most loyalty programs. The site also reviews and ranks the programs and posts the latest frequent-flier news, such as United's recent decision to set a stricter expiration policy.
Honorable mentions: Petersen also runs http://www.flyertalk.com, for those who want to talk to others about frequent-flier programs, and http://www.insideflyer.com, a subscription-based magazine and Web site for the miles-addicted. Athttp://www.frequentflier.com, you can download software for consolidating your loyalty program information, while http://www.milemaven.comis a good place to go for information on mile promotions.
Guidebooks. It's difficult to pick a favorite in this crowded field because each one gears itself to a different demographic. But my pick for general info is Frommer's ( http://www.frommers.com/); the site offers all the basics (how to get there, best time to travel, hotels, sites, restaurants, etc.) plus good entries on recommended destination-geared reading and recommended hotels in categories such as "best for a romantic getaway" and "best historic hotel." It books trips through http://www.travelocity.com/.
Honorable mentions: At http://www.fodors.com, you'll find all the basic info plus quirky features; its London guide, for example, includes articles on a trip to Abbey Road and "Arts for Free." Backpackers will find plenty to like about http://www.lonelyplanet.com.
Hotels and other lodging. One of the most comprehensive sites is Hotels.com ( http://www.hotels.com/), which says it offers rates from more than 70,000 properties worldwide. The 15-year-old site sorts properties by name, star rating, price and its own picks, and it contains detailed info on each hotel, with map locations. It also now states total charges with taxes before you enter credit card information. Users who feel uncomfortable booking online can get the same deals by calling its toll-free number (800-246-8357). Weak points: Its condo/vacation home rentals are thin, and you must prepay.
Honorable mentions: If you're interested in quainter or more upscale lodging within the United States, try http://www.quikbook.com, which recently added shortcuts that allow users to search for smoke-free hotels and green hotels. Go to http://www.searchparty.com for downloadable software that compares hotel prices from various sources, including most major hotel sites. Register with http://www.hotelbook.com for offers on independent hotels. To locate rent-by-owner properties, try http://www.vrbo.com, http://www.cyberrentals.com or http://www.forgetaway.com, recently launched by the Weather Channel.
Insurance. Several sites that compare travel insurance options allow you to see prices, to compare coverage and to buy, all in easy-to-use formats. But QuoteWright ( http://www.quotewright.com/) is a cut above only because users can easily locate the policies' fine print; the site, for example, explains under "trip cancellation" who would qualify as a family member in case of emergency. It includes results from all the major companies, including Travelguard, Access America and CSA Travel Protection.
Honorable mentions: You can also compare results with http://www.insuremytrip.com and http://www.quotetravelinsurance.com.
Jets. It may not be the most useful site, but a new player, Flight Explorer ( http://www.flightexplorer.com/), sure is fun. Install its software and you can view a specific flight in 3-D with satellite maps beneath it. Want to know what city, or even what block, it's flying over right now? Just zoom in. Who knew that United Flight 209 from Washington Dulles to LAX flew directly over Vermilion, Ohio? The site also has more useful functions, including the 15-day on-time performance record for specific flights.
Honorable mentions: For checking out airline seating before you get stuck next to the bathroom, try http://www.seatguru.com, http://www.seatexpert.com and http://www.lovemyseat.com. For rankings, ratings and opinions on the airlines, airline lounges, airports, etc., go to http://www.airlinequality.com.