(STK) is a fast and fun kart racing game that you can play with kids, parents or significant women in your life. STK is completely free and open source. The latest major version was released last month, so start start your tinkering.
Try it Today
Current Roadmap http://supertuxkart.sourceforge.net/Milestones
For Developers http://supertuxkart.sourceforge.net/Get_involved
Making Karts http://supertuxkart.sourceforge.net/Kart_resources_index
Making tracks http://supertuxkart.sourceforge.net/Track_Maker%27s_Guide_2
Using Blender as a map editor http://supertuxkart.blogspot.kr/2012/04/blender-as-game-editor.html
Appropriate for ages 5+
Over 20 tracks and battle arenas
Weapons, obstacles, and powerups
Split-screen multiplayer support for up to 4 players
Many game modes
Available on GNU/Linux, Windows, MacOSX, FreeBSD, Solaris
Built using the Irrlicht game engine
Supports gamepads (the xbox360 controller works great)
You can join the community and start coding, making art, music, animations, designing new karts and tracks and bug testing. They are looking for help adding new game modes, individualized physics for each kart, adding AI to battlemode and getting internet multiplayer working. They want to polish up the art style and make it more consistent and adding new sfx, textures, and models.