Quadplex Scrabble
Online Scrabble game. Play for free as a guest or enjoy the benefits of membership such as no ads, rating, forums and chat, robot opponents, statistics and tournaments.

Online-Scrabble.com
Online scrabble plysite where you can play 'traditional' 'never ending' scrabble games.

The Pixie Pit Scrabble
Play free e-mail Scrabble. Supports two, three and four player games. Also has chat and a forum.