Port Scanning with Nmap: The How To

Tutorial Article Nmap: A valuable open source tool for network security by Michael Cobb.
I found this article very useful to learn more about the general Scanning fundamentals.
See how to spoof ports, fragment packets, scan to determine the Operating System, and save reports to your computer.

The Reference Guide to Nmap
http://nmap.org/book/man.html

This is a site with helpful tips. This is a page is associated with the above page.
http://nmap.org/book/man-port-scanning-techniques.html