Are you interested in "really serious" games, something in
the order of 1 move per day? Then I recommend to try out
http://www.playchess.de :

- Play many games in parallel
- tournaments (5, 7 or 9 players)
- Classes for players of different strengths
- Analysis room: analyse your game and discuss it
- rating calculation
- Advanced chess (optional)
- performance and opening statistics
- casual (social) games
- PGN downloads
- friendly atmosphere, much fun, but serious games

http://www.playchess.de

Thomas

PS: don't trust me - I'm the webmaster. You better check out yourself... ;-)