There's going to be lots of Silverlight playing over the weekend for me :D 

Microsoft have released the source code for all of the Silverlight controls as well as almost 2,000 unit tests with this. 

One of the best things about this is they have a unit testing framework for Silverlight.  It's a great way to not only help develop but be able to start creating your own great Silverlight controls.

I think the web teams at Microsoft have been sensational this year with plans to release the ASP.Net MVC Framework and source as well.

Shawn Burke has a post walking you through the source code and test suite. 

Thanks to Brad Abrams who is fast moving up my list of favourite blogs for news. #1 at the moment fyi is Coding Horror.

Jeff Wilcox has a post detailing the Unit Testing framework he built for Silverlight 2.