For my SANS GPEN Gold certification (first Gold-certified analyst for GPEN -- go me!) I wrote a paper on my SMB scripts for Nmap. The paper is titled "Scanning Windows Deeper With the Nmap Scanning Engine". I started writing it a few months ago, and collaborated with Fyodor in the early stages. Hopefully it's a useful guide!
I talk a bit about the theory and protocols behind the scripts, then dive into a few of the more interesting ones and talk about how they work and how they can be used.
Let me know what you think!