Last week Mary Jo Foley hinted at it. (She must have good sources!) Now the news is out about the Dynamic Language Runtime for .NET.
John Udell has just posted a podcast with John Lam from the Dynamic Languages team at Microsoft that they recorded last week. John Lam was the creator of RubyCLR before he was hired by Microsoft last year. Since that time, Lam's been working in secrecy on what is now known as the DLR.
The Dynamic Language Runtime is what makes it possible to develop Ruby & Python applications on .NET.
You can find the podcast on Channel 9 here.