For a while now it's been possible to configure Visual Studio to allow you to step into the publicly available source code for the .Net Framework, but a post on Channel 9 today provides information on some new ways to get at this fascinating information MS are releasing.
The one that caught my attention is that MS have released an online browsing tool to allow you to look through the public source in your browser. Perfect for those "why does it do that?" moments you hit every so often when developing.
Take a look for yourself at http://referencesource.microsoft.com/
There's lots of information about all the features they're releasing, plans for the future and the ways it can be used on the .Net blog at http://blogs.msdn.com/b/dotnet/archive/2014/02/24/a-new-look-for-net-reference-source.aspx
I'm off for a read...