The Model View ViewModel pattern has become very popular for building WPF applications.  Until now, there wasn’t much guidance/tooling from Microsoft to help you get started with MVVM.  The WPF team just released an early preview of the MVVM Toolkit:

“The Model-View-ViewModel toolkit is intended to introduce the Model-View-ViewModel design pattern for building WPF applications to the broad WPF developer community.
The toolkit includes:

• A Visual Studio 2008 template (Visual C# Express 2008 also supported)
• Documentation
  • General introduction to M-V-VM
  • Walkthrough using the VS template
• A complete WPF application demonstrating the M-V-VM pattern

You can download the toolkit on the WPF Futures page.”

I just installed it, went through the documentation/walkthrough.  I’d definitely recommend taking a look at this!

I hope there is something like this in the works for Silverlight:).