Here is the much blogged about Scott Hanselman's list of great .NET developer - interview questions. Broken up into the following:

• Everyone who writes code
• Mid level .NET developer
• Senior developers / architects
• C# component developers
• ASP.NET (UI) developers
• Developers using XML
  

What Great .NET Developers Ought To Know (More .NET Interview Questions)

(linked to from Chris Sells "Interviewing at Microsoft" page here)