I've been doing a little research on starting a rescue too. There is a lot of good info out there. Here are some links:
PetRescue.com - Lots of good stuff on how to find dogs and legal things that go into starting a rescue.
Start A Rescue - Another site full of information
Matching Dogs with People - How to match up potential owners with rescues.
There's a lot of work that goes into starting a rescue. Hopefully this helps you.