Hi, I hope you find what you're looking for but I have to say that if you're searching specifically for PhD forums, unless there's something I've been missing, I've found them very thin on the ground.
As already mentioned, the best idea is probably to google for subject specific forums... even though many users of them probably won't be PhDers. Best of luck to you and wherever you go - and hope you don't come across too many people posting rubbish. There are some real idiots out there!