RATTWorks (http://www.rattworks.com)
West Coast Hybrids (http://westcoasthybrids.homestead.com/home.html)
Sky Ripper Systems (http://www.skyrippersystems.com)
Propulsion Polymers (http://www.propulsionpolymers.com)
HyperTEK (http://www.hypertekhybrids.com)
AeroTech (http://www.aerotech-rocketry.com)
Micro Hybrid (http://www.hpr.org.uk/mhybrid)