I have just passed another Microsoft exam - this time it was related to the technology I truly love - WPF
It was 070-502 (Microsoft Certified Technology Specialist: .NET Framework 3.5 WPF Applications).
51 questions and 2,5h time for all of them. Quite demanding compared to other exams I have taken.
I was preparing for this exam mainly with the book WPF Unleashed
by Adam Nathan and Daniel Lehenbauer (who was one of the key WPF developers). I encourage you to try it - astonishing book!