Raymond Chen, one of the key developers at Microsoft (he's been around for aaaages), has one of the better geeky blogs on the net. If you have to develop on the Windows platform on a day to day basis you should check it out.
One of his recent posts dicusses spam - he's tracked every dodgey email and virus that has ended in his inbox and created a graph depicting when it arrived and how big it was.
The way such a mass of data is presented in such a digestable way would make Edward Tufte proud.
The result is fascinating, and there's good news; spam seems to be reducing...