I still have my first AOL account from when we first got internet in 96 or 97. That said, I haven't gone on it or AOL in probably 10 years.
Aside from that, I've been a registered member on a Star Wars forum (lucasforums) since 2002. It used to be a flourishing community, but now it is pretty dead. There are still a few regulars that post and I check in now and then. I think the earliest forum I joined was sometime in 2001, but one of them reset their user database and shit awhile ago (it was some Zelda forum... still around, but I can't remember which one).
And, funny enough, I've used "ZBomber" as my internet alias ever since that Zelda forum. So I guess this is the 10th year anniversary of my user name.