Modern Microprocessors: A 90 Minute Guide
There's also a book from an Ars Technica guy covering modern processors in an approachable way:<p><i>Inside the Machine: An Illustrated Introduction to Microprocessors and Computer Architecture</i><p><a href="http://nostarch.com/insidemachine.htm" rel="nofollow">http://nostarch.com/insidemachine.htm</a>