I'm a member of One Piece Bay, but I don't post a ton. Mainly because I rarely have anything to add and I don't RP.
Technically i've been a long-lasting member on Zelda Universe and Naruto Forums, but i haven't really logged on either site for quite some time now.
I've been on other forums before, but was never active on any forums until becoming a fan of Friendship Is Magic and joining friendshipismagic.org - flowing over to Equestria Forever when some past mods of FiM.org decided to start a new site. I thought it looked more friendly and promising. I've been on MLPforums but haven't really used it much because I'm not into such big groups, I prefer somewhat smaller communities where it's easier to get to be known by... well, everyone. Lately I've been feeling the need to branch out a bit more (and get away from EqF a little bit), and was happy to be directed here. Creeping up on three weeks since I've joined and I must say they've been great.
Here and MLP Forums are the only forums I frequent these days. I'm kind of torn between the two because MLPF's larger community = more active users, but EPF's smaller community = more tight-knit. I've looked at a couple of other pony forums before, but they didn't seem like all that in a bag of potato chips. May join another in the future, though, if I run across something that looks appealing. Aside from pony-related forums, I used to be an active member on Final Fantasy Alpha, Gaia Online and Dreamviews Lucid Dreaming forums. I believe my account still exists on the latter, so I could probably still access my old dream logs if I wanted to.