Since the dotnet source code are avaible now, including WPF, it's a good chance for us to read the code and go deep.

So, I will write a series of article descring something found in the code.

You can get more information on how to get the source code at:

http://blogs.msdn.com/sburke/archive/2008/01/16/configuring-visual-studio-to-debug-net-framework-source-code.aspx

And there is a tool called NetMassdownloader(http://www.codeplex.com/NetMassDownloader). This tool can help you to

get source code without Visual studio.

And there is a great article you need to read when be ready to use NetMassDownloader
Download All the .NET Reference Source Code at Once with Net Mass Downloader http://www.wintellect.com/cs/blogs/jrobbins/archive/2008/02/06/download-all-the-net-reference-source-code-at-once-with-net-mass-downloader.aspx

 Thanks to John Robbins bringing us this great tool!