Shawn has put together a great sample site showing a Silverlight client consuming the REST based data services provided by Astoria. And he's even made the source code available. Nice job, Shawn!
theADOguy - Rant: Silverlight + Entity Framework + Astoria == Crazy?
By the way, thanks again to Shawn for helping me answer questions at the recent MSDN Event covering Astoria and Silverlight.