I was just reading through the Hidden Features of C# thread, and there were a lot of really neat tricks that I had never even heard of. But there wasn't really a whole lot of depth to them all. It got me to wondering what kind of books and tutorials are out there that teach more advanced topics (Delegates, Lambdas, Threading, etc) and advanced tricks.
What books and tutorials have you all read that have helped you learn some more advanced tricks and features?