Craig Shoemaker posted two awesome webcasts on MVVM in both Silverlight and WPF with some help:

(Craig Shoemaker) decided to create some long-form screencasts that will help teach the concepts of MVVM. I contacted Microsoft Program Manager Tim Heuer to tackle the Silverlight project and WPF Super Ninja Josh Smith to lead the way for a WPF implementation.

As to why he did this, he explains:

With the emergence of WPF, the change in architecture brought about a need to shift the approach of separation of concerns in the presentation layer. The approach of Model-View-Controller and it’s offspring were an obvious choice, but the existing models were required no small amount of shoe-horning to make a comfortable match for XAML applications.