www.gunzonline.com it's got an awesome game there called gunz
www.tibia.com - a free non pay mmorpg
www.travia.com - dunno how to explain it but it is a game to keep running in the background while playing other games
www.runescape.com - an rpg
Flash games
www.arcade42.com
www.fukgames.com
www.gamevera.com
www.hallpass.com
www.laststopgames.com
www.notdoppler.com
that's about all i can think of