MiniClip
A web-site with a huge range of online games of all sorts: puzzles (including Sudoku), multiplayer games, etc.
Web-Sudoku
An online Sudoku game, with 4 difficulty levels. Also has some variants of the game.
FreeOnlineGames.Com
A large range of online games of all types.
FreeWorldGroup.Com
A large range of online games.
SmashinGames.Com
A large range of Flash based online games.
GameGecko.Com
A large range of online games.
Net-Games.Biz
A large range of online games.