Earlier in Oct. I had posted about .NET Framework Source Code to be Released, and it was a big news.
And now it has been made available as Scott Guthrie announced it on his blog. Check the blog for details. This will be valuable to developers.
Also check Shawn Burke's blog post for instruction on how to install this for VS 2008.
One can post questions on Reference Source Server Discussion - MSDN Forum if one is having any problems related to it.