- Citizen scientists, one of whom unearthed a whole mammoth skull from a 25,000-year-old South Dakota sinkhole
- A logging-town kid who grew up to lead service trips for The Sierra Club, which start at $315 for a week, including all meals
- A retired military man who became a fish-identification expert for REEF and now undertakes research dives for aquariums, universities, the park service, and the National Oceanic and Atmospheric Administration
- My pal Charyn Pfeuffer who traded luxury-lifestyle coverage for a year of voluntourism projects around the world
- Lillie Marshall, the seventh-grade Boston Latin Academy instructor behind TeachingTraveling.com, which encourages instructors eager to trade their briefcase for a backpack, but also to travelers who want to venture into far-flung classrooms
For further ideas, pick up a copy of The Frugal Volunteer (Dog's Eye View eMedia, 2012) by my dialed-in colleague Nola Lee Kelsey.