National organizations:
National Association of Rocketry (NAR)
Tripoli Rocketry Association (TRA)
Forums/places to get information:
The Rocketry Forum
Rocketry Online
Ye Olde Rocket Forum (YORF)
Essence’s Model Rocket Reviews (EMRR)
Data, plans, and software:
Jim Ball’s Scale Library of Missile Data
JimZ’s Rocket Plans
Ye Olde Rocket Plans
RASAero (Free)
RockSim ($)
SpaceCAD ($)
Visual Center of Pressure (VCP) 1.64 (Free)
Winroc (Free)