I play on 2 sites.
My favourite is http://www.chess.com as it allows me to talk to the people I play against, live and without restriction. You don't have to pay to join, unless you wish to.
The other is http://gameknot.com. This site has lots of restrictions on free members though. You can't talk to the people you play against and it seems a bit impersonal. I don't know what the paid membership provides though.
