Academy of Model Aeronautics - Worlds largest sport aviation organization

A.M.R. Productions - Warbird (giant scale), Jet, vintage r/c society

Ernie Hubers R/C Flight Training Center - Learn to fly with Ernie Huber!

International Miniature Aircraft Association

R/C Flight Unlimited - Howard Sullivan's very useful website with lots of good information

RC Online - A based messaging site, but slow

RC Universe - A very complete web based messaging site with tons of information

RC Plane Reviews - Kit reviews, RC articles, Prop charts, help for beginners

National Society of Radio Controlled Aerobatics - AMA recognized SIG 

RCMicroFlight - Newsletter covering park & slowflyers, and indoor radio control modeling

ScaleAero - E'zine promoting the sport of flying scale models

The E Zone - Great web site for electric flight