This is the first big thing I worked on in the ASP.NET team, the release of the ASP.NET MVC Source Code to Codeplex. Scott Guthrie announced this  a few minutes ago and as he says it's the first of a number we have planned over the next while.
What is surprising is how much time and how many people it takes to pull a release like this together...but I really think it's the start of something really amazing and to quote a corny phrase 'you ain't seen nothing yet!'