Link: http://www.igl.net/monop/
Link: http://www.casesladder.com/browse.php?game=Monopoly
Case's Ladder is not actually a site where you can play Monopoly online. It's more of an added feature, a way for some players to have more fun playing Monopoly -- and it's definitely not for casual players.
This site features Monopoly (and many other board games) in ladder and tournament formats. If you're not familiar with ladder competitions, they rank competitors over a period of time. When you beat someone you move up half the distance between their rank and yours. So if you're #100 and beat #1, you move to #50.
The Case's Ladder site includes Monopoly ladders for players at Games.com and Playsite.com, in addition to players using the Westwood Monopoly CD-ROM.
