Tim Keller & Urban Mission (Lausanne)
Here's a short 18 minute video on urban mission. Keller gives 10 characteristics of contextual churches.
You can also download his urban mission paper. Here's a quote from that paper.
"Biblically, an experience of saving grace through evangelism leads to radical sharing of wealth and helping the needy. And when the world sees this sharing, that there is “no needy among them,” (Acts 4:34) it leads to more powerful evangelistic witness (Acts 4:33). Thus doing justice and preaching grace go hand in hand, not only in the experience of the individual Christian but also in the ministry and effectiveness of the urban church."