Composite Application Guidance with updates for Silverlight 3 is now available on MSDN. Get it here
From project page
Note: This is a minor update to the February 2009 release. This release includes:
- Projects refreshed to target Silverlight 3.0
- Changes in DelegateCommand and CompositeCommand to no longer hold on to CanExecuteChange handlers.
- The TabRegionControlAdapter was updated to set the context for the Header item to retain the same behavior as Prism 2.0.