This article is from the Model Rockets FAQ, by Wolfram von Kiparski with numerous contributions by others.
Some of the competition kit OEMs and component manufacturers include:
Apogee Components http://www.apogeerockets.com/ Balsa Machining
Service http://user.mc.net/~bms/ Edmonds Aerospace
http://members.aol.com/RobEdmonds/Edmonds.html Pratt Hobbies
http://www.pratthobbies.com/ Qualified Competition Rockets
http://www.cybertravelog.com/qcr/ Totally Tubular
In addition is a *wide* listing of competition kit resellers and scale
kit OEM's, too many to properly include here.