Forget the tan, the Mickey Mouse photos and the cliche souvenirs.

These days, travelers want to experience something more than the gated resort and the cruise ship buffet. They want to go on a walking tour, climb a mountain and kayak down a river -- adventures that can make a vacation more meaningful.

"In travel, people are increasingly seeking the authentic unique experiences that stretch the imagination and create potent memories that last a lifetime," said Chris Doyle, vice president of the Adventure Travel Trade Association. According to the organization, adventure travel is the fastest growing segment of the leisure travel industry.

Of course, adventure is in the eye of the traveler, and ranges from a walking tour to whitewater rafting. But because of that, it remains relatively unaffected by the weak dollar and economic downturn, said David Larkin, managing director of AdventureUs.com, a social networking and directory for adventure travelers.

Here, according to the experts, are some of the latest trends in adventure travel.

Volunteering: Combining volunteerism with vacation continues to be a growing trend; Global Volunteers saw a 30 percent increase in participation last year, according to co-founder Michele Gran. Baby boomers still rule, she said, but the fastest-growing demographic in the past couple of years has been people under age 20, more than likely baby boomers who bring their children with them.

Expeditions: More people are helping researchers through the Earthwatch Institute, an international volunteer organization supporting science. Expeditions include surveying coral reefs on a remote Bahamian island or feeding and caring for cheetahs in Namibia. Most of the trips are two weeks, and no special training is required. (Exceptions may be trips that require scuba-diving certification or a high fitness level). Other examples include conservation-minded tours to watch giant sea turtles lay their eggs in coastal areas of the southeastern U.S., Mexico and Costa Rica.

Charity: Think an extreme version of a walkathon. Venture Expeditions, a Christian-based organization, sponsors trips to raise awareness and funds for various organizations, such as biking through Thailand to raise money for an orphanage. Travelers pay for the trip and then make a minimum donation to the charity.

Adrenaline rush: Some people call action-packed vacations "The Bucket List" for the movie starring Jack Nicholson and Morgan Freeman, two terminally ill patients who want to complete a list of things to do before they kick the bucket.

Ultimate 5 Lifetime Adventures packs five of what it calls the world's greatest adventures into one week: a military-developed Ropes Challenge Course, skydiving, Indy car racing, rappelling and piloting a primary combat trainer aircraft.

Family way: Some families (including multigenerational) are forgoing theme parks and all-inclusive resorts for "more genuine nature-based, cultural, and education and learning excursions," Doyle said. He attributes this in part to baby boomers who have the means to travel "coupled with a strong interest in bonding more deeply with families." GordonsGuide.com, a Web site on adventure and active travel, reports that the top vacation requests are all family friendly -- dude and guest ranches, houseboat rentals, whitewater rafting and horse pack trips and trail rides.

Easy does it: An increasing number of people are choosing a vacation that centers around a theme, such as a culinary tour in Asia or wine vacation in Israel. Yoga has also seeped into the mix. Best of Both Women's Adventures has yoga on all of its trips and a specific yoga and surf vacation in Puerto Rico. (Surfing is one of the top activities that women want to do, said Dez Bartelt, co-founder of Best of Both Women's Adventures.) Other combinations include yoga and snowboarding or yoga and wine tasting.

Exotic cruises: Travelers are becoming more interested in expedition cruises to Antarctica, the Galapagos and Alaska, said Carolyn Spencer Brown, editor in chief of CruiseCritic.com.

The cruises, while less glitzy than big-ship cruise lines, include lectures and presentations about the place. "On an expedition cruise, everything revolves really around what you see off the ship," says Brown. "On the big-ship cruises, everything revolves around what happens on board and the ports are sort of an addendum."

Roots search: With an increasing number of people swabbing their cheek to find their roots, some are taking it a step further and traveling to the places where their ancestors lived. Discover Natural Ancestry amazingdna.com) not only provides DNA analysis and genealogical services, it puts people in touch with tour operators who plan the trip for them. "If they are breathing, then they have a genetic story hidden within them, and we help them to discover and explore the unknown secrets about their heritage," said Yvonne Walker, marketing director for Discover Natural Ancestry.