"Voluntourism" closely follows ecotourism as the next hot travel trend. The idea is just as it sounds - combining volunteering with travel, as a way to give back, meet locals, learn a skill, save the world...It has its negative nancies just like anything else, but for the most part, voluntourism really is a great idea. Treehugger recently named working on organic farms as the best volunteer vacation in its "Best of Green 2010: Travel and Nature."
You can meet local farmers while harvesting rice in Japan for example, or growing mangoes in Belize. There are a number of reputable travel companies offering volunteer vacations - we'd recommend Projects Abroad or BaseCamp International.
But do your research! Unfortunately, there are a number of unsavory characters out there more than happy to take your money. Our friends over at Verge Magazine are a good place to start if you're keen. And they're really nice - promise ;)