As of yesterday, the ASP.NET MVC Release 2 source code
has been made available on CodePlex
made the source drop announcement
earlier this morning. Congrats to Phil Haack
and the ASP.NET MVC Team for shipping the source code. It's worth noting, it's not Open Source in the way that it's just a zip file and no outside patches are to be accepted, unlike IronRuby. The plan going forward is to make incremental drops of the source code going forward.
As always, check out Jeffrey Palermo's MVCContrib project
for contributions to the code base, which is open source.