This weekend a group of person release the first beta version of the WP7Contrib component. This component provide some helper which help simplify WP7 development. They also included some UI controls.
This component is build to work seamlessly with MVVMLight. They integrated some other framework like JSON.NET, Silverlight Serializer and Reactive Extensions for .NET (Rx).
Let give a try: http://wp7contrib.codeplex.com/