Microsoft have finally announced the first stage of the DBP competition over at http://www.dreambuildplay.com/main/HowToPlay.aspx

Quote Originally Posted by Microsoft
Warm-Up Challenge – Relatives of Spacewar
Create a game based on the Spacewar Starter Kit— either the Spacewar codebase or content, or both. The only requirement: Your game must be derived from the version of Spacewar that’s a part of XNA Game Studio Express. Use as much or as little of the Spacewar Starter Kit as you like. Just remember that the relationship to the Spacewar Starter Kit must be obvious to our judges.
They are offering $500 (USD) to the top five entries!

You've got until the 2/28/07 at 11:59:59 PM CT to get your XNA entry in.