Gamma Low is an interesting new multiplayer RTS project. Players act in teams in some kind of light oriented battle. It is very early in the project and the only worthwhile information seems to be in their roadmap, but it's an intriguing concept nonetheless.
Hex-a-pop is an original and well implemented puzzle game with cute graphics. Once you get your head around the basic techniques used to consume common hex patterns, it's pretty easy, but I think it's a good game for spatially challenging a younger audience. And it's open source and available for most operating systems.
There's a new Open City screenshot, seen here on the right. How cool is that starting to look, eh? New release soon? Fingers crossed.
I mentioned the space sim Stress Free Zone for the first time a few weeks ago, a space combat game which aims to have cooperative multiplayer gameplay (e.g. defending space stations) as well as modular ships among other features. They are making good progress too, which can be seen on their development blog.
And last but not least Windstille 0.3.0 is out in the wild. A platform game in the style of the classic Turrican series, the game now boasts 3D characters running around an artistic 2D world. Currently it is only distributed in source format but is still only more of a tech demo than a game. It is hard to find any screenshots but I have seen it in action and it looks really nice.
I'm sure there's more but my brain is in "off mode". I still did not get Privateer Gemini Gold 1.02rc1 running (well, it runs, just without sound) on my Ubuntu Feisty Fawn laptop although I did help one of the main developers fix a few setup issues. Did anybody else have more success?