.NET RIA Services a framework to simplify the traditional n-tier application pattern for rich internet applications. Although it has been clearly targeted for use with Silverlight the infrastructure works through the DomainServices set of classes and can be used from within a .NET WebForms, MVC based application or since DomainService speaks in a standard restful manner it may be accessed from many other client technologies such as Ajax.

I have currently only glanced over RIA Services, however, from a brief look it does seem quite an elegant solution to what are both common and ugly problems. Of particular interest to me is how validation is supported using meta data in the business layer and how easy it should be to plug in a testing framework to perform unit tests against the application logic. The feedback received from the community seems to also be very positive so far so I really do think that this will be a project worth taking a look at.

Brad Abrams has wrote a brief introduction on RIA services and some downloadable samples can be found on the Microsoft downloads site.