Microsoft Patterns and Practices group helps us build WP7 apps that are testable, MVVM and shares an "Advanced App Case Study"...

Microsoft Patterns and Practices Phone Development Center

Summary

How do you build applications targeting the latest generation of Windows Phone 7 handsets?

Smartphones are advanced computing devices that allow users to install and use advanced applications that capitalize on the features of that specific device. Although developing applications for phone-based devices was once a specialized skill, today developers are able to use their existing desktop skills and familiar desktop tools to create smartphone applications.

Active Releases

• Developing a Windows Phone Application using the MVVM Pattern.
• A Case Study for Building Advanced Windows Phone Applications.
• Building Testable Windows Phone Applications.

...

Microsoft Patterns and Practices Phone Development Center - Developing a Windows Phone Application using the MVVM Pattern

Microsoft Patterns and Practices Phone Development Center - A Case Study for Building Advanced Windows Phone Applications

Microsoft Patterns and Practices Phone Development Center - Building Testable Windows Phone Applications

Some cool and useful guidance and information the MS P&P team for WP7 dev... I

(via  Chris Koenig - P&P Windows Phone Guidance Released)