Nigel Sampson has published the first post in a series about the Model, View, ViewModel pattern (MVVM).
The focus this series is going to take is keeping the pattern "Blendable" i.e. making sure we can take advantage of the tooling support in Expression Blend and that we don't interupt the designer / developer workflow.
I'm also not going to try and present the full system all in one step, we'll start simple and build up to a full working application.