On my trip to Bolivia with Compassion I came across an organization called Mission Year (MissionYear.org). Oreon Trickey was one of the Compassion artists on the trip, and she's on staff with Mission Year.
In a nutshell, Mission Year is, as the name implies, a year of mission work in an inner city. Missionaries raise their own support, with a goal of $12,000 for the year. One of the goals is to live as simply as the poor they are serving, so they only have direct access to $60/month after rent.
I just had lunch with David Malcolm, who is the son of my parents' friends. He's spent his year volunteering (they can't receive an income) at a church and public school in Philadelphia's inner city. He was able to facilitate a Bible study at the school, where he saw God moving through David's efforts.
To contribute to Mission Year go to MissionYear.org. If you'd like you can designate David Malcolm or Oreon Trickey.