My colleague Bob Familiar has a nice series on the subject:

This series of articles takes a look at the current state of RIA development leveraging Silverlight 2. The series will focus on the architecture of RIA's, the use of XAML for resolution independent user interface layout and design, Windows Communication Foundation for Web Services, Visual Studio 2008 and Expression Blend for the design/development environment and Windows Server 2008/IIS7 as the deployment environment.

Some great SL2 resources as well...take a look!

Bob's Blog : Silverlight 2 and Rich Internet Applications