I believe that lots of people have watched the keynote speech given by Scottgu at MIX 09 conference. In Scott's demo, he showed fairly quick and simple implementations for multi-tier Line-of-Business applications in Silverlight, using a Microsoft framework called .Net Ria Services.
I, as a tester, am so proud of being a member of the .Net Ria Service team. I really hope what we do can make you, the web developers' lives easiler.
In compliance with Silverlight 3 beta, we released the Microsoft .Net Ria Services Preview at Mix. It is free and can be downloaded here: