Well, this one snuck up on me. I hadn't heard about this project before Mix, unlike the Silverlight & Dynamic Language Runtime which I had known about for quite some time. The ADO.NET team announced project "Astoria" yesterday at Mix.
"Astoria" enables applications to expose data as a data service via the web using simple REST-like interfaces. (GET, POST, PUT, DELETE). Data is transferred in either XML or JSON format. This new data service layer will certainly make it easier to build the "Web 2.0"-type of applications we're seeing these days on the web.
For more information on "Astoria" plus the beta bits, go here.
Also see Pablo Castro's blog too.