National and International
Canadian Association of Rocketry http://www.canadianrocketry.org/
National Association of Rocketry (NAR) http://www.nar.org/
Tripoli Rocketry Association http://www.tripoli.org/
Local Clubs (just some of many!)
Ottawa Rocketry Group http://ottawa-rocketry.org/
Pittsburgh Space Command http://www.psc473.org/
Upstate Rocketry Research Group http://urrg.us/
Maryland Delaware Rocketry Association https://mdrocketry.org/
Northern Virginia Association of Rocketry http://novaar.org/drupal6/