Gameland has a great selection of arcade, board, strategy, puzzle, sports, action, and card games. You will have to sign up with the website before you can play any of the games.
Shockwave has a great selection of, you guessed it shockwave games. The site has action, arcade, and creative games that are quite different from other sites. You will have to download shockwave onto your computer before you can play most of these games.
Games.com is a website full of board & word games, arcade games, and card & dice games. This site has all the big name games that you will want to check out if you have a fast computer.