the beta download for XNA game studio express is out!
this is the software designed for the Xbox 360 creator's club
update: xnaspot.com is a great place to start with XNA GSE.
"XNA Game Studio Express enables individuals and small teams to more easily create video games using new, optimized cross-platform gaming libraries for Windows and Xbox 360. This beta release targets the development of games for Windows. The final version of XNA Game Studio Express will be available this holiday season and will enable development of games which target Windows and upon purchase of a XNA Creators Club subscription, the Xbox 360 as well."