I used to play Gemstone 3, best MUD evah, and I believe the original Gemstone was one of those games you could play on AOL waaay back in the day (before unlimited access, of course).
Speaking of fun games, for the trader in you AOL also had Federation (www.ibgames.com). $12 a month (not worth it IMO) but it was a fun game esp. while it was free...Fed2 is in beta right now, free access, and I've been having fun with it. The problem is the game doesn't get good until you've made a couple of ranks (the game gets really great when you get your own planet!), the start is slow and the beta only goes so far now...So the best stuff isn't play-testable (or they're not going to play-test it...). But if you remember Fed, swing by for a few rounds.
But if you're looking for best MUD evah, Gemstone.