Microsoft has released ASP.NET MVC 2 Preview 2.
Amongst the new stuff added like the ModelMetadata and ModelMetadataProvider Classes, HTTP Verb Overrides, Single-Project Areas and much more, I find the support for the jQuery validation library to provide client-side validation, the most interesting bit in this release. This version can work side-by-side with ASP.NET MVC 1
Here are some important links:
Download ASP.NET MVC 2 Preview 2
Download the Release Notes
Download the Source Code on CodePlex
If you are new to ASP.NET MVC, you can read this ASP.NET MVC - Some Frequently Asked Questions