The XNA team have just posted a request on their blog looking for people to submit XNA games:
We’re looking for a few 2D and 3D games created using XNA Game Studio for an upcoming opportunity to showcase the great work our community has been doing since we released the tools over a year ago. This could be the chance you and your game have been waiting for to enjoy the spotlight and anything that may come as a result. You will additionally have a chance to participate in an upcoming closed beta of a new XNA technologies.
Submissions are due in by January 18, 2008. Full details can be found here: http://blogs.msdn.com/xna/archive/2008/01/07/calling-all-games.aspx