Steam Greenlight is a system that enlists the community's help in picking some of the new games to be released on Steam. Developers post information, screenshots, and video for their game and seek a critical mass of community support in order to get selected for distribution. Steam Greenlight also helps developers get feedback from potential customers and start creating an active community around their game during the development process.
Pro Greenlight Concepts section can help get early feedback
The Concepts section of Greenlight allows incomplete projects to be put on display and receive feedback, including mock-voting as if they were full Greenlight submissions. This can be a valuable tool for refining design, presentation and marketing techniques.