Propulsion Directorate, Air Force Research Laboratory  
   Information on their research projects, and a propulsion primer
   http://www.pr.afrl.af.mil/

A & E Engineering  
   Some advanced propulsion concepts described.
   http://www.up-ship.com/AandE/AandE.htm

Beginner's Guide to Propulsion  
   Tutorial slides on basic propulsion concepts.
   http://www.grc.nasa.gov/WWW/K-12/airplane/bgp.html

Chemical Propulsion Information Agency  
   Comprehensive site with technical resources, propulsion papers, meetings and events calendar.
   http://www.cpia.jhu.edu/

Compreactive Propeller (Airscrew).  
   It is suggested to use the internal space (internal channel) of a rotating blade as a centrifugal flow pump delivering pressurized air in a jet engine located on the blade tip.
   http://shulga.tripod.com/compreactive/E.htm

Journal of Propulsion and Power  
   Site contains a searchable Table of contents and information for authors and subscribers.
   http://www.aiaa.org/content.cfm?pageid=177

Rocket Science Institute  
   Offers texts about rocket propulsion and propellants, from black powder pyrotechnics to NASA-scale systems.
   http://rocketsciencebooks.home.att.net/catalog.html