In conjunction with the release of the XNA Game Studio Express, GarageGames is also releasing their Torque X game engine based on XNA that simplifies game development considerably. Get Torque X "Open Beta" here:

For more information on Torque X, visit the Torque X Landing Page.
For more information on XNA Game Studio Express, visit the Microsoft XNA Page.
Fore more information on the XNA Creators Club, visit the Microsoft Creators Club Page.