I've looked at a few, but The Session.org is the only one that I've found to be consistently worthwhile, with some really sound advice and lively discussion couple with excellent accessibility.
For me, the worst has to be the BBC board - inhabited by warring tribes of imbeciles and trainspotters and moderated by dolts. Those who want more moderation here, think on't and ponder!
Thanks to all for the other suggested links, though - I shall look foward to exploring them.