After 5 previews finally Microsoft released beta version of ASP.NET MVC.
You can download ASP.NET MVC Beta
"The ASP.NET MVC Beta release provides a new Model-View-Controller (MVC) framework on top of the existing ASP.NET 3.5 runtime."
Learn more about ASP.NET MVC
Microsoft ASP.NET team also working on
Dynamic Data | WebForms | Dynamic Language Support | ASP.NET QA