At MIX '09, together with the announce of the Silverlight version 3 era, an interesting new project was announced to the public: Microsoft has released the first public CTP of .NET RIA Services (formerly codenamed Alexandria), along with a basic first walkthrough of using it.
As explained by Microsoft, .NET RIA Services simplifies the traditional n-tier application pattern by bringing together the ASP.NET and Silverlight platforms. The RIA Services provides a pattern to write application logic that runs on the mid-tier and controls access to data for queries, changes and custom operations. It also provides end-to-end support for common tasks such as data validation, authentication and roles by integrating with Silverlight components on the client and ASP.NET on the mid-tier.
.NET RIA Services simplify Line of Business (LoB) RIA development. They complement the existing Data Access Layer and presentation components in the .NET framework and Silverlight. They build on the foundation of ASP.NET and codify, evolve and support some of the common patterns in web applications.
I've done a quick read of the first walkthrough released and this project seems really interesting... we'll see more in the next months.