I'm currently slogging through Prism, the MSDN sample app for demonstrating Composite Application Guidance patterns.
Intended Audience
This guidance is intended for software architects and software developers building enterprise Windows Presentation Foundation (WPF) or Silverlight applications. The Prism Library is built on the Microsoft .NET Framework 4.0 (includes WPF) and Silverlight 4 (previous versions support .NET Framework 3.5 and Silverlight 3), and it uses a number of software design patterns. Familiarity with these technologies and patterns is useful for evaluating and adopting the Prism Library.
It's a big bag of overkill for simple apps (as their HelloWorld sample elegantly proves), but contains lots of good examples for designing larger-scale apps with WPF clients (both desktop and Silverlight).