Rick Byers, who works on the CLR's DevServices (read: debugger) team recently started blogging. Today he writes about a topic that comes up every month or so on our internal mailing lists, covariance and contravariance of CLR generics (read: why can't I cast List<string> to List<object>?).
In other link propagation news, Keith Brown has two new articles up on MSDN, the first being a very good introduction to CAS. He describes evidence, permissions, and the basics of the policy engine and the admin UI. His second article is last month's Security Briefs column from the MSDN Magazine, where he creates a managed interface to the Windows ACL editor. The current version of his wrapper doesn't support Whidbey's new built-in support for ACLs, however he promises an update when we get closer to shipping.