0 A.D. is a game like Age of Empires 2(RTS and 4 resources). Is open source (GPL) and promises to be good.
Good opportunity for animators, modelers and programmers in C + + give their contribution to the project.
I love Age of Empires 2. 
Official website:
http://os.wildfiregames.com/
News release of alpha:
http://www.phoronix.com/scan.php?page=news_item&px=ODUyNQ
Fórum:
http://www.wildfiregames.com/forum/index.php?showforum=135
Wiki:
http://trac.wildfiregames.com/wiki
Interesting question:
http://trac.wildfiregames.com/wiki/WfgAcademiaInto
"Why should you as a developer, hobbiest, student or a professor be interested in using Pyrogenesis?
- The game itself is visually attractive as delivered. Instead of the all too frequent “programmer’s art”, you have quality artwork at your fingertips that allows showing your project in its best light.
- WFG has taken great pains to emphasize history through out development stressing authenticity and accuracy; always remembering the educational opportunity we have in games.
- The software is portable (running on Linux, Windows, and MacOSX).
- The code and design are well documented (comments, CppDoc documentation, Wiki, some full technical reports, reams of forum posts with rationale and discussion).
- The project is made up of gamers / people looking to get into the industry; a good deal of experience in this area has been gained and can be passed on.
- One of our goals is that this project will gain some traction with the public as development progresses. You as a contributor would be able to point to a well recognized development project that has a tangable release of software.
- Templates to assist in creation of art assets (textures, meshes) will be provided.
- Various tutorials and guides will be available for ease of initiation."