When you hit this site, go here . Now, these trips aren't exactly free. But you get to monitor the endangered black rhino in Kenya for 15 days, food and lodging included. Young and old from all over the world gather to plant orchards, build schools, protect the environment, improve health care and foster worldwide peace. There are camps in Japan and Bangladesh in Asia and also in Australia and the Middle East.
Work camps offer an inexpensive way to travel, live and work internationally.
I'm about to leave on my third. Cross-cultural Solutions , is another way to go. They also offer the opportunity to travel and learn about the people and cultures of Cuba, Ghana, India and Peru through their Insight Programs. Most of the volunteer programs are three weeks long. If you decide you like this type of travel, they have longer programs with the Insight plan.