Probably this one. I like seeing what people have to say about things other than Pokemon. Don't get me wrong, I'm still a fan of the games and such. But the anime has gone way downhill and the new fans who just came in during Diamond and Pearl or HGSS need some serious therapy in the ways of the old Pokemon if they think it's all that nowadays. I don't really hang out there anymore.
Occasionally, I browse the Fanfiction section. But that's only because I like to beta read and such. I would post some of my fanfiction, but I won the award for Fanfiction of the Month back in 2005 and for some reason my Pokemon-writing mojo just kind of...disappeared after that. I might get a good idea. I don't know.
But yeah, those are the two forums I spend the most time at.