I stumbled on an excellent article in the O'Reilly ONDotnet.com site that explains the factory design pattern using the FCL. This is a paradigm that I would highly encourage and may be taken from Microsoft's explanation of the Factory pattern. I would argue that this article is even better than the MSDN articles on the .NET implementations of the Observer, and Singleton patterns, because it goes beyond the abstract and shows actual examples in the FCL.
It would be wonderful if someone (Brad Abrams) could produce a listing of patterns and their implementations in the FCL. I, for one, wish to implement patterns the way the FCL does.