For a long time the busy gift shopper has been able to pick up the phone and order a last-minute bouquet of balloons or a singing telegram to honor birthdays and anniversaries.

Add now to the list of possibilities the dial-an-adventure travel gift. With only one shopping day left until Christmas, it could be the gift to complete your holiday list.

It's the unusual idea of McLean lawyer Marsha K. Greenfield, who in the past year has given up her legal career to develop a variety of adventure gifts in the Washington, Ft. Lauderdale and San Francisco areas.

Say you have a hard-to-please brother or a sister who has everything. For $125 a person, you can buy them an hour's hot-air balloon ride over the Virginia hunt country on any day of their choice. If they happen to live in California (or are traveling there), the balloon floats above the Napa Valley wine country.

The firm, Adventureline, mails either the gift-giver or the recipient a gift package that includes a personalized certificate, a full description of the adventure, directions on how to go about setting the date and a sky-blue Adventureline T-shirt. (For this Christmas, you could write your own note indicating a certificate is in the mail.)

Recipients have until the Nov. 15 following the purchase date of the certificate in which to use it, so they can pick the season.

Among the 18 gifts available within the Washington area: a flight in a sailplane ($70); copiloting a helicopter ($85); a two-day cross-country ski weekend in western Maryland ($190); white-water rafting on the rapids at Harper's Ferry ($65).

But personal gift-buyers aren't her only customers. Companies have begun to buy the trips as employe bonuses, she says.

Greenfield got the idea when she had to buy a gift for her sister in California. She settled on a singing telegram but wasn't really satisfied with the choice. About the same time, her husband treated her to a spur-of-the-moment, first-time ride in a glider.

Even as a once-only thrill, she had a "dynamite" flight. Wouldn't it be nice, she thought, "to package up adventure"? Shortly thereafter she did just that, beginning last March. Since then, she has expanded to Florida and California and expects to add two or three more destinations each year.

Her adventures are all for beginners "to see what it's like. We're not out there to terrorize people." She figures there are a lot of people, like herself, who "want a few thrills in life." She has become very aware of "the growing trend in adventure travel."

In her case, with the glider flight, "I just wanted a chance once in my life to fly," she says, and then adds, "and to tell people I have flown. Sometimes that's the best part."

Initially, she expected Yuppies, young two-career couples "like my husband and myself," to be her best customers. So far, though, it has been women in their forties and fifties "buying for their husbands in their forties and fifties." The minimum age for a recipient is 10.

The actual trips are provided and supervised by experienced outfitters, licensed pilots and guides with whom Greenfield has contracted. All flights, she says, are arranged through flying schools, and the craft have dual controls. Only one recipient so far has rejected the gift, because of a fear of flying. In such cases, the money is refunded.

For more information: Adventureline Inc., P.O. Box 3211, McLean, Va. 22103, (703) 790-5195.

* STUDENT TRAVEL: Finding the right summer camp, student trip abroad or study program for your youngster can be an intimidating and time-consuming labor. The choice of summer travel opportunities for children is large, and parents must consider cost, the quality of the program and the special interests and talents of their youngsters.

Help is available from an organization called Tips on Trips and Camps, which has evaluated about 400 summer programs for youth, including tennis and other sports camps; music and art camps; wilderness treks in the West and both language-study and long-distance bicycling trips in Europe.

Throughout the school year, the group arranges Washington-area open houses in which representatives from its approved list of youth programs are available to distribute literature, offer slide presentations and answer questions. Usually between 30 and 40 summer camps and tour organizers attend each open house.

Tips on Trips and Camps also maintains a local phone number, where parents can learn what kinds of camps and tours are available and what the cost of each is.

The organization was founded 14 years ago in Baltimore and now has offices in nine cities, including Washington. Its services, including consulting and open houses, are free to parents; it receives a percentage fee from the camp or tour organizer when a child is signed up for a program.

Open houses scheduled for January:

* Bethesda-Chevy Chase High School, 4301 East-West Highway: Saturday, Jan. 12, from 1 to 4 p.m. in the school cafeteria.

* Vienna Community Center, 120 Cherry St. SE, Vienna, Va.: Sunday, Jan. 13, from 1 to 4 p.m. St. Andrews Episcopal School, 8935 Bradmoor Dr., Bethesda: Saturday, Jan. 26, from 1 to 4 p.m.

Summer camps and travel opportunities are available for children from ages 7 through high school, with a few programs for college-age students. The cost can vary from $200 to $300 a week for a camp to several thousand dollars for an eight-week program abroad.

Last year, the local organization registered about 550 students from the Washington area, says Nancy G. Ludewig, one of the local group's three consultants. Some parents enroll their children in a European program and then tour Europe themselves so they can be nearby.

The camps and other programs recommended by Tips on Trips and Camps are evaluated, among other things, for safety, quality of program, ratio of instructors to youngsters and financial soundness. Camps in which the instructing staff is predominantly adult are preferred, Ludewig says. So are camps where a large percentage of the staff returns each year.

Each camp is visited at least once every three years, says Beatrice L. Levi of Baltimore, the organization founder. Returning students are surveyed, and complaints are investigated. Recently, a participant wrote that the promised training in advanced sailing was not offered.

"That's a flag to me," says Levi, suggesting the camp may be slighting other advertised activities, as well. If it proves true, she will drop the camp.

Levi developed Tips on Trips and Camps after studying summer programs for her two sons, both of whom are now adults. So many people began phoning for advice, she decided to incorporate. For students today, as it was for her sons, her goal is find the right program for each child.

Summer travel for the young, she says, can be "an eye-opening, awakening opportunity."

For information: (301) 530-3313.

* SHAKESPEARE'S ITALY: Folger Theatre is celebrating its 50th anniversary season with a two-week escorted tour of "Shakespeare's Italy," March 19 to April 2. The itinerary includes Venice (home of Shylock of "The Merchant of Venice"), Verona ("Romeo and Juliet," "Two Gentlemen of Verona") and Rome ("Julius Caesar," "Coriolanus," "Antony and Cleopatra").

The price is $3,101 per person (double occupancy), which includes air fare, motorcoach travel, hotels, certain meals, guided tours to historic attractions and a $350 tax-deductible contribution to the Folger.