http://users.commkey.net/Braeunig/space/propuls.htm Rocket propulsion formulas (High School and above)
http://library.thinkquest.org/12145/propul3.htm?tqskip1=1&tqtime=0706 Propulsion Efficiency of a Rocket motor (high school level)
http://lekstutis.com/Artie/PEP/ a software program for determining the characteristics of different propellant formulations. (college level)
http://seed.mainecenter.org/application/files/packets/PDF100.pdf How to build your own rocket engine thrust stand. (high school level) [cached]
http://www.allstar.fiu.edu/aero/rocket1.htm Introduction to Rocket Performance. An excellent site that mostly describes real rockets, but it is just as applicable to model rockets.
http://www.LUNAR.org/docs/handbook/motors.shtml Primer on rocket motors. How they work, how they are classified, sizes, NAR Certification list, and how to insert igniters.
http://www.dnaco.net/~dantassi/motors.html Dimensions of all certified model rocket motors.
http://www.irving.org/rocketry/types/ Explaination of the different types of rocket motors, from small size to the bigger ones. (elementary level).
http://www.irving.org/rocketry/igniters/ Rocket motor igniters in the presence of strong radio waves. Some safety concerns you need to consider when handling rocket motors, ejection charges, and igniters.
http://home.swbell.net/sbaughmn/propulsion.html Description of the components in composite propellant motors, particular emphisis on reloadable motors.
http://www.geocities.com/CapeCanaveral/Cockpit/1938/data.html Software for designing rocket motors. Very technical.
http://www.cosrocs.org/articles/cato.html Explaination of the term "CATO," and how to prevent them from occuring.
http://members.cox.net/rpmachining/Rockets/page%2004.htm Designing a Liquid propellant rocket engine (College Level)
http://www.atf.treas.gov/explarson/fedexplolaw/index.htm BATF Orange Book of Federal Explosives laws. These laws pertain to the chemicals that are used to make model rocket motors.
http://www.cmass.org/radiocmass.html sounds of rocket motors
http://www.bookcase.com/library/faq/archive/model-rockets/ignition-tips.html tips for igniting motors, including staging composites, clusters, and other high-tech methods. Text only.
http://www1.iwvisp.com/thehalls/rockets/faq24/ Unique propulsion systems used in real rockets.