PRISM 4 (aka Composite Application Guidance for WPF and Silverlight) is Available

Prism 4.0 has been released!!!!

Overview (from MSDN download site)

Prism provides guidance designed to help you more easily design and build rich, flexible, and easy to maintain Windows Presentation Foundation (WPF) desktop applications and Silverlight Rich Internet Applications (RIAs) and Windows Phone 7 applications. Using design patterns that embody important architectural design principles, such as separation of concerns and loose coupling, Prism helps you to design and build applications using loosely coupled components that can evolve independently but which can be easily and seamlessly integrated into the overall application. Such applications are known as often referred to as composite applications.

WHAT'S INCLUDED IN THIS RELEASE (from the read me file)
The following assets are shipped with Prism 4.0:
· Signed Prism Library for Windows Presentation Foundation (WPF) and Silverlight
· Signed Prism Library for Windows Phone 7
· Batch file to create custom Prism Library binaries
· Batch file to register the Prism Library binaries with Visual Studio
· Model-View-ViewModel Reference Implementation (MVVM RI)
· Stock Trader Reference Implementation (Stock Trader RI)
· Prism 4.0 documentation
· QuickStarts:
o New or updated QuickStarts in Prism 4.0:
- Basic MVVM QuickStart
- MVVM QuickStart
- Modularity QuickStarts (with MEF and Unity)
- State-Based Navigation QuickStart
- View-Switching Navigation QuickStart
- UI Composition QuickStart
o QuickStarts ported from Prism 2.x:
- Commanding QuickStarts
- Event Aggregation QuickStarts
- Multi-Targeting QuickStarts
- Hello World QuickStarts

Get it here.

Check out the documentation here.