I haven't played in ages, but
http://www.isketch.net/ used to be a lot of fun - it's an online Pictionary-like game...
Psychobabble on pop-cap is also a lot of fun --it's an online game that y ou play wiht more than 2 people -- basically you are given a bunch of random words (like like those refridgerator magnets) and you ahve tocreate a sentence out of those words... players vote on the best sentence and you can't vote for yours-- plus there's a chat feature (sometimes you get the idiots who just want tocyber but if you get in a good room, it's a lot of fun)