Learn about Union (a platform for building multiuser applications) and MegaPhone (a hosted service for developing multiuser big-screen games you control with your phone) in these two recently posted presentations:
Multiuser Adventures at FITC
>> http://www.fitc.ca/media/?video=Your_phone_is_your_controller-C_Moock.flv
Your Phone is Your Controller at MAX:
>> http://max.adobe.com/online/session/116