let's see...
- Shadow's Lair (slowly dying)
- The Semi-Pro Gamer Lounge (still active, for mkwii semi-pros)
- Dragon Matrix (same as Shadow's Lair)
- Global Conflict (since the flaming from one member, I don't/won't go there anymore)
- Marriland Forums (dunno why I don't go there anymore)
- Serebii Forums ( ^ )
- GameFAQs ( *has 427 karma and joined june 22 07* yes, I still go there)
- Forum Lagoon (for all the lagoons. ex gaminglagoon, cashlagoon, scubalagoon, cubelagoon. etc.)
- dungeon.filb.de (is not advertising, that's the name of the site) (WAS, closed down)
- My own forum called "Competitor" (died out a long tiem ago)
- Here
think I got all of them
I used to be active just on Pokemon Fan Universe quite a bit, but I left there on two occasions due to reasons I won't discuss here.
I also have an account on every Pokemon forum you can think of(because I wanted to be Alakazam if and when I became active, XD). Of those the only one I go to besides PC is Serebii. But I only go there for WiFi battles if the WiFi Forum here is dead.
I bet you don't have an account on Dragon Matrix. :p