The Gaming Den: I'm just a member there, but I like it. Basically, we discuss roleplaying games. We criticise them for any minor problem, as a way of alerting people to the problem so they needn't discover it themselves, but we also come up with solutions. Many supplements are made for D&D there, specifically "How to put up with the stupid shit WotC made, and balance stuff again." and "Okay, by the standard rules, here's something strange. Let's assume the world actually includes that, and see what happens."
Also, unlike the WotC forums and all, we're allowed to use the word "fuck". This is more important than you think, what with all the rants, such as those on anyone involved in 4th Edition, and whatever. We're currently making our own new edition, with a deadline of "Before 4E comes out" and with a goal of "Less time. Less people. Let's make it better than whatever they make. That way, they have no excuse, and we can play something we all helped make and properly playtest. Something that's as close to perfect as it can get."