Hard to remember exactly. I started on rec.running, then I was on DRS and CVRT listservs for years stating early 90's, even running the CVRT list off one of my servers for a while when the main one crashed. DRS was cool back then, when John Parker, Hal Higdon, Don Kardong, Jon Sinclair, etc, all posting fairly regularly. It's also how John Bingham got started, well before he was in RW. I still have a copy of the old "bindlestiff and gandy-dancer" thread that was legend.
CoolRunning was cool for a while, as was the competitive running forum on RW. When the competitive running forum changed platforms and coloring got bought out, MERV got started and I hung out there until the right-wing crazies pretty much took over and it stopped being a running forum (like what's going on here now).
Around then someone sent me a link to a thread on letsrun, and I've been here on and off ever since. It would have been about a year or so before Hope died (the person, not the attitude), so if any former MERVites remember when that was it would give me a date. I'd guess 2000 or before, since I think one of the brojos was trying to get his OT time in the 10K.