I remember posting on the very first thing that Eric had - you couldn't call it a message board, it was more like one long page with indentation showing the replies in a thread - a little bit like a newsgroup listing I suppose. I registered as my real name and felt a bit strange when everyone else was using monikers (ones I particularly remember at the time were Cyberzombie, Forgotten Hater, Crypt King and Ruin Explorer, as others have mentioned). I remember the first time that one of my observations was quoted and seconded by CZ, I felt so proud
When Eric moved to his first real messageboard, I decided to register with a moniker and life has been, uh, Plane Sailing ever since.
I remember when Henry (C'mon August!) first started posting on ENworld, having seen him on the WotC newsgroups. I remember when Piratecat first started posting about 3e as an insider (no rules broken, just encouragement!). and when his first storyhour started (The galley crewed by minotaur pirates was heading at ramming speed towards their vessel... Velendo jumped overboard holding his stone shield into its path and activated the shields "immovable object" property, leading to splintering of the minotaur galley. I remember thinking "Blimey, that all sounds a bit over the top").
If I worked out exactly how much time I'd spent on these boards it would probably be frightening. On the other hand, I've met some really nice people in real life as a result of them, not to mention lots of nice people in this virtual world. Still the best online community I've ever seen.
Cheers