Gyroscopes As Propulsion Devices
Gyroscopes have many uses, this site explains how a gyroscope works and what they can be used for. The site also looks at the possible uses of gyroscope based propulsion (gyroscopic propulsion).
http://www.gyro-scope.co.uk/

Advanced Topics in Aerodynamics
Electronic media about Aerodynamics, Aeronautics, Propulsion Systems, and Related Technology.
http://www.aerodyn.org/

Space Exploration Nuclear Propulsion
A tutorial on zero-g aka microgravity and why it is not zero gravity.
http://www.astrodigital.org/space/nuclear.html

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

JPL Thermoelectrics
Comprehensive information source about the technology and its applications from the Jet Propulsion Laboratory (JPL) of the California Institute of Technology (CALTECH). Includes history, scientific background, and device overview with animated illustrations.
http://www.its.caltech.edu/~jsnyder/thermoelectrics/

Advanced Space Propulsion Study: Antiproton Annihilation Propulsion
Advanced Space Propulsion Study - Antiproton and Beamed Power Propulsion: ANTIPROTON ANNIHILATION PROPULSION.
http://www.transorbital.net/Library/D001_S01.html

AC Propulsion, Inc.
Manufacturer of battery and propulsion systems for electric vehicles.
http://www.acpropulsion.com/

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

Beginner's Guide to Propulsion
Provides information on propulsion for the K-12 audience.
http://www.grc.nasa.gov/WWW/K-12/airplane/bgp.html

ePower and Propulsion
Power, Propulsion, propulsion and power, Gas Turbines, Rocket Propulsion, Space Propulsion, Automotive Propulsion, Electrical Propulsion, Space Power, Aerospace, NASA
http://www.epower-propulsion.com