http://www.themediacenterproject.com/KinectForMediaCenter
Does not currently support the XBOX Kinect, just the Windows Kinect device, though someone will change that I'm sure... but a great start.
Kinect for Media Center is an application that interacts with my Media Center Remote Command Listener to control a Media Center computer using Hand Gestures and Voice Commands, utilizing the Kinect for Windows hardware. The Hand Gestures and Voice Commands control the Media Center interface, as well as any add-ins running inside Media Center. This includes popular add-ins such as Netflix, MyMovies, Media Browser, and Heatwave.
Does not currently support the XBOX Kinect, just the Windows Kinect device, though someone will change that I'm sure... but a great start.