http://www.tuxgames.com (commercial)
they sell mostly games from the sadly closed Lokigames.com
don't expect good support from them - they are useless
but there is a big title of commercial (mostly old) games to choose from.
http://www.legendsthegame.com (free)
I don't know *why* they haven't put the link to download the Linux version.
But there is one - go to fileshack.com or similar and look for Legends for Linux
you will have to do an update also (please forgive me - I lost the code!)
so search their forums too.
http://www.vendetta-online.com (commercial)
That is a MMORPG style of a game, if you like that sort of stuff - they give you 1 month trial.
Yes it is commercial - dont give them grief they are nice people.
Uplink (commercial)
http://www.introversion.co.uk/
EnemyTerritory (free)
You would download that from FileShack or any such place. Don't forget to download the updates.
American Army (free)
http://www.americasarmy.com/
To some this is the best game ever that runs on Linux.
I don't know I found it hard to put up with a seargent shouting at me
Savage for Linux
http://www.fileplanet.com/files/130000/131247.shtml
To find more games try searching tuxgames.com or happypenguin.org
or fileshack/fileplanet with the keyworkd Linux.
Also,
I am
desperately seeking a copy of Tribes 2 for Linux
I am willing to pay for the CD retail price.
I am finding it impossible to find a copy anywhere in the web