Spend your off hours defending the universe against the Shivan threat, get Freespace: The Great War
Other stuff you should already know about:
Freespace 2 - http://icculus.org/freespace2
D2X - http://icculus.org/d2x
Tux Games - http://www.tuxgames.com
Linux Games - http://www.linuxgames.com
Someday there will be something really, really cool here... someday, maybe.