http://www.happypenguin.org/ – frequently updated list of linux games. Not all of them are good, but some are nice.
http://www.lgdb.org – Linux Game Database. Has less games, but nice games. Also has a link for single click ubuntu install, which installs game without running synaptic.
A http://www.gunnerkrigg.com cute comic about small girls which attend to school which is kinda different.
Game looking just like Starcraft but done only by 3 people. It is now in its final version, containing 6 levels, nice graphics and playability.
2D game in developement – http://tery.mypage.sk/