I signed on to Kiva, a microloan organization, sometime last year. Through a small (less than $50) investment, I helped to fund two different projects in Africa. I chose which ones, and helped women expand their small businesses to take care of their families. The first loan was completely repaid on time, so I funded a second one.
Kiva sent me a link where you can get a $25 free starter credit, funded by the Kiva board member Reid Hoffman (founder of LinkedIn). There are a limited number of credits available, and last time I got a link, they were gone by the time I posted. I just clicked and they are still available at this time. If you're interested, take advantage now, here. The free credit is only good for new lenders.