Kazama is a Pygame-based fighting game engine. [video] It's young and performs rather slowly and the license status of the media included in it's first release is somewhat dubious.
There has been an update of the First-person shooter Retribution Engine: Some weapon tuning and two maps. To my knowledge the game still only compiles on windows machines which is unfortunate, as it appears to include a map and a model editor, which might be worth a look.
LPairs is a memory game which uses graphics of the Tango Desktop Project. It's just as exciting as every other memory game and I must say that the best thing about it is the user interface library (pretty fading menu fonts). This is something all the LGames shine in.
I also just found out via the news planet, that OpenAnno appears to have it's first playable release! And they made a video!!
Mono.XNA is an open source, cross-platform implementation of Microsoft's XNA gaming framework. So far I had to ignore the 84 SourceForge.net-hosted XNA-related projects. This might change now. Thanks to SiENcE for the tip!
[Edit] On the other hand, the project doesn't seem too active really. Last SVN commit Jul 25, 2007.