Kiva.org allows people to make $25 loans to low-income entrepreneurs in the developing world (microfinance). By doing this, we can help provide affordable working capital for the poor (money to buy a sewing machine, livestock, etc.), empowering them to earn their way out of poverty. I first learned about this organization on a PBS program a year ago. Here is some info on a business:
There are not very many open projects to fund right now due to a lot of recent publicity by Bill Clinton - in his new book Giving and by Oprah. Definitely take a look at some of the funded projects around the world.