I really enjoy this online version of the game Settlers of Catan by Mayfair Games. You'll need Java and an ISP that won't cut you off if you sit on one page for too long.
The Look and Feel New Media web site has games under the Portfolio menu bar item. You'll be surprised how addictive they can be, especially Make-a-Flake.
The Nabisco World web site has some games, but you'll have to register to keep high scores or to enter any of the contests.
I like a few of the games at Pogo, and the advertising time-outs give you time to rest your fingers.
I don't play any online games that require money (yet).