There is a new
WCF RIA Services QuickStar with lots of screenshots and code.
Source: Silverlight.NET
WCF RIA Services simplifies the development of n-tier solutions for Silverlight applications by enabling you to coordinate application logic between the server project and the client project. RIA Services provides framework components, tools, and services that make the application logic on the server available to the client without requiring you to manually duplicate that programming logic. This QuickStart shows you how to add a domain service to the server project and read from that service in the Silverlight client. Next, it shows how to restrict data modifications to authenticated users. Finally, it shows how to add validation logic in the server project that is automatically enforced in the client application.