As I'm working on my NAnt implementation, I came across Eric Desch's article published on the 4 Guys From Rolla site titled “A Brief Introduction to NAnt”. He does a very nice job of providing an introduction to NAnt along with a rundown on how to get the software running. He discusses NAnt, NAntContrib and MSBuild and provides links to some applicable resources.
I wish I had this intro when I started with NAnt, it would have eliminated some initial wheel-spinning. If you're considering NAnt or looking for a starting point, this article is a nice resource.