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.
The Fantasy & Sci-Fi Books, Movies and TV forum. I read way more than is healthy for me, and am always looking for new book recommendations and discussions on the ones I've read. Same goes for movies.
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.
I think I like the d20 OGL and Publishers forum second best, because I can find all sorts of news and previews there, including answers from the publishers themselves.
I'm down with the story hour forum. Its great reading, but it angers me that I can't write as well as most of them, and with such staying power. Darn you Pkitty!!!!