At
Scott Hanselman's Weblog you can find two sets of questions he believes to be common knowledge for any decent .NET developer.
The first set has some general questions for any ASP.NET developer.
The second set is insane. Plain nuts, if you ask me, but somehow I still agree with him. From a personal perspective I don't know the answers to half of these questions (as I write this), but I can see why I should.
So I've decided to spend more time investigating what goes on "behind the scenes" of whatever I am developing.
It obviously wouldn't hurt...