Just to say, please consider an older dog instead of a pup or very young dog. The young-uns get homes very easily and the poor slightly older dogs can sit there for ages. When I worked at Battersea we had so many lovely lovely dogs who I would have taken home with me in an instant if I could have, who just sat in the kennels for anything up to a year for no good reason except that nobody would give them a chance because they were older than others!
Heres a link to a rescue which always has new dogs looking for homes, some ex breeding ones in a really sorry state.
http://www.freewebs.com/manytearsrescue/dogslo okingforhomes.htm
Good luck with finding your dog, you will love having a rescue dog, I have 2 and it's so great to know that you are giving a home to a dog that really needs one.