I shall be brief, for I am in my briefs, and briefly available to briefly brief you.
It's like Command and Conquer. Except it's good. See video:
Rising up... mmmmm mmmm... took my time took my chances... aaaah ooo... just a man and his will to survive... nmmmm mmmmm... its the Eye of the Tiger!" Gotta love that track.
There's a new development release of Oolite, the elite-inspired game. Version 1.72 (announcement, changelog) has been a while coming and, as such, contains a long list of fixes. Looks pretty stable to me but *shrugs* not my project.
FreeCol 0.8.0alpha3 - fixes a few bugs, they say.
Vacuum Magic is R-Type style 2D side scrolling shoot 'em up action, and all Free Software. The game topic is a little off beat but the gameplay is pretty neat and there's plenty of levels to play. Check out the video:
Open Octane, announced in the forums, aims to be a fast paced car combat game where you can destroy most things in the game world. You can see the car crashing through trees and fences in the demo below:
It reminds me of another open source game that I can't remember right now as it's late and I have other things to do. I'm sure I'll remember later or somebody will post in the comments the game I'm thinking of...