buildthatgame.net is an experiment to make content and concept of a game completely based on the community. Fundamental ideas of gameplay are choosen and designed by the community. The users decide which features are worth to implement and which aren't. The most voted features will be implemented by a small development team and everyone can download the game at any state of development for free. It is very hard to get such a project going and therefore it would be great, if you take part.
Give it a try and visit www.buildthatgame.net