Hybrid Rockets
Hybriddyne Forum: Great Hybrid Resource
Matthew Leung's Firekiss Project
MB Rocketry Mike Bennett's site dedicated to information on rocketry including model, high power and amateur rockets along with experimental motors
Jimmy Yawn's Recrystallized Rocketry
Amateur Icelandic Rocketry Forum
Digi-Key: Electronic Parts, fast service.
Thunder Valley / HighQualityChems.com Pyro Chemicals.
CP Technologies: Amateur rocketry book, software and video.
Firefox: Chemicals and rocket supplies.
Online Metals: Small quantity metal shop.
McMaster-Carr: Huge online hardware store.
Yazoo Mills, Inc.: Cardboard tubes by the case.
Graphite Store: The name says it all.
Metal Express: Nice selection of larger stock, locations nationwide for faster service.
Grizzly Industrial, Inc.: Online/Retail tool supplier. Great selection/prices.
allorings.com: O-rings of all types and sizes under the sun, info on application and compatibility.
Speedy Metals: A recent find. It looks like they have a nice selection of larger product.