I probably check at least briefly in about half the BBS forums, which is a lot to keep track of, so I might have to narrow in sometime in the near future.
In addition to checking in here, I still enjoy most of the Trek forums, but then again, I haven't been around (the BBS, that is) as long as some of you, so I still enjoy the General Trek, TOS, TNG and DS9 discussions. I don't always post that much in any of those - it kind of goes in fits and starts - but I like to at least check and see what folks are talking about these days, and in particular I like to see what the people I like are talking about. And sometimes a particular topic will catch my interest.
Same thing with the TV & Media and Science Fiction & Fantasy forums, really.
Edit: I visit the VOY forum regularly, too, but I don't post very much, for some reason.
The general movie forum and the XI forum...nah, not so much. I not only don't have much to say on those - I mean, I have enjoyed several of the movies, but I am not passionate about any of them - but I also don't understand what anybody else can find to say, either.
Every now and then, I'll read the Trek Lit forum, but I very seldom post. I just recently started checking the fan fiction forum, but that's because I was cajolled into participating in the October challenge - which was more fun than I was expecting, BTW.
I would like to participate in the Trek Tech forum, because I do find the science of Trek interesting, but I am a science dabbler, and frankly, those guys are just to techie for me. Or at least they write as though they are.
I avoid TNZ as though it were infectious. Maybe it is?