Channel 9 turns one year old today, and to celebrate they've been releasing quite a few interesting interviews. One in particular that really stands out is the four parter with Windows Kernel Architect Dave Probert. Dave gives an overview of Windows organization, design decisions, and lots of ways that Windows solves different problems. Along the way he gives various comparisons to how Unix operating systems approach the same issue, specifically referring back to his BSD roots. If you're interested at all in how Windows works under the cover, this is a nice introduction. People more familiar with how Windows works will find this mostly an overview, but I still found some of the comparisons and anecdotes Dave shared to be interesting.
Another good spot they've got up is an interview with Eric Lippert, who was actually the second interview to ever appear on Channel 9 (Bill Hill was the first). About 25% into this interview, Eric begins giving a 30,000 foot overview of CAS and then digs around through various other managed security issues, such as:
One of the more interesting points he mentions is how VSTO refines the default CLR security policy, for instance by saying "being granted FullTrust via the Zone and AllCode membership conditions, is not good enough."