My favorite charity is the International Justice Mission. They free slaves. Literally. They free slaves and prosecute slave-holders in order to bring them to justice. When I was a Senior in college I heard the Intl. Justice Mission's founder speak at the Urbana 2000 Conference and I have never forgotten his story. For me it defines the Christian life and calling. You can check it out here: http://www.urbana.org/archives/2000/30th-pm - Click on the Gary Haugen link.
Of course I want to be clear that I'm not under the impression that bringing light into dark places and fighting slavery is the sole territory of Christians. We all need to work against evil in the world and if you are a person who does not believe that slavery should be eradicated get the frak away from my blog!
Check out the IJM's work at their website www.ijm.org or check out the video below for more info on what they do.