Benjamin J. J. Voigt posts what seems to be a very valuable .net resource: ARK 3.0. Lots of cool and interesting articles in there, including presentations and other goodies.

In first glance I really liked these articles:

• Scripting .NET using Mondrian
• Design and Implementation of Generics for the .NET Common Language Runtime
• Stack Inspection: Theory and Variants
• MSDN Wonders of WinForms column: More WinForms Multi-Threading

lectures:

• .NET Enterprise Services (audio)
• A Tour of the Shared Source CLI Distribution (video)

There are also full books and sample book chapters for download:

• .NET Framework Security (full book)
• COM and .NET Component Services (Sample chapter 10)
• Building Secure Microsoft ASP.NET Applications (Sample chapter 8)