Try http://www.bigroadblues.com I've only just found it myself and have yet to check it all out, but the guys on the forum all seem to know what they're talking about.
I've started to muck around a bit with slide at the moment. I'll be changing the strings on my acoustic from 11-50 to something like 13-56s and my slide from copper to ceramic.
See you there,
Shane
