What: Earthwatch Institute matches would-be research assistants with scientists who are studying animals and their natural habitats. A volunteer might record the behavior of wild horses on the Outer Banks of North Carolina or tag terrapins off the coast of New Jersey.
Duration: Most trips last two to 17 days.
Volunteers pay: $950 to $2,650, including meals and shelter, which varies wildly, from tents to country inns (EarthWatch.org)
Grow your life! Get an exclusive look at Oprah's new farm, uncover 28 fresh ideas for happier living, and learn Bob Greene's top secret to eating smarter. Plus, find out how you can win a trip to Hawaii to have lunch with Oprah!