Prism (Composite Application Guidance for WPF and Silverlight) 2.1 - October 2009 is designed to help you more easily build enterprise-level Windows Presentation Foundation (WPF) and Silverlight client apps. It'll help you design & build enterprise-level composite WPF client apps—composite apps use loosely coupled, independently evolvable pieces that work together in overall app.
The guidance includes a reference implementation, reusable library code (named Composite Application Library), documentation, QuickStart tutorials, and hands-on labs. This version of Composite Application Guidance is designed to help you build WPF and Silverlight apps that've a single code base.
More Info: Download