I like the Storyhour forum, simply because Piratecat, Sepulchrave, and the Jester post the stories of their group's adventures there (Piratecat's originally being the one that drew me over here from the WotC boards to ENWorld).
My favorite forum is D&D Rules because a) there are a lot of knowledgable people that can help me to interpret the rules, and b) I can see debates on what is too powerful/not powerful enough that are intelligent.
PLaying hte game and talking the talk, because I get to play there. Second to that are the publishers forums. It gives a chance to see cool stuff coming out, open calls and the e-publishers forum is filled with all sorts of great info.