I had a long coffee with HandUp's founder Rose Broome, who's done a boatload of legwork in this space (and just had Jason Calicanis ask to lead an investment round). Was intro'd to her product by a homeless guy in my hood and immediately had to know more. It's the first piece of tech that really wowed me with regards to making some headway on some of these issues - I'd highly encourage anyone who thinks about the space a lot to connect with her team. They're pretty responsive @handup on twitter.

http://streetlifeministries.org/ is run by an ex-homeless (David), you can ask him.