The Official National Site:
http://www.scouting.org/Commissioners.aspx
The Grand Daddy of all Unofficial Commissioner Sites:
Advice for Commissioners:
Ask Andy from NetCommish
By David Frydenlund, Pacific Skyline Council
Training Materials, Outlines, Powerpoints:
http://netcommish.com/training.asp
Online Courses
A Good Introductory Course from NetCommish
http://netcommish.com/resources.asp