Recently Microsoft released Composite Application Guidance for WPF (for VS2008 and .NET 3.5).
Quote: “The Composite Application Guidance for WPF is designed to help you more easily build enterprise-level Windows Presentation Foundation (WPF) client applications. This guidance will help you design and build flexible composite WPF client applications—composite applications use loosely coupled, independently evolvable pieces that work together in the overall application.
The Composite Application Guidance for WPF can help you split the development of your WPF client application across multiple development teams. In this type of application, each team is responsible for the development of different pieces of the application, which are seamlessly composed together. The guidance includes a reference implementation, reusable library code (named the Composite Application Library), documentation, QuickStart tutorials, and hands-on labs.”