I only remember stuff vaguely but one of the first boards I was at was Mortigi Tempo (sp), a Radiohead message board on greenplastic.com.
My username was Angel first and Creep later on (that was a bad idea xD)

Then I was at lilymud.net, a TLK fanart message board back in 2001, my user name was Nala-the-lioness (my artist name at the time). I left but I'm back there now as Xander ^^

Then there was, umm FFInsider. My user name was Xander there I think.

I joined a harvest moon board while I was playing it, Xander again there, that was a little while ago.

Others include The Basement which I joined last year sometime, a pixel art forum, a HTMl forum, lots of other random ones I didn't post at much.

Now I only post regularly here, a litle at Lilymud and very occasionally at the basement.