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

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 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

HobbySpace - Launch, Propulsion & Spaceflight Systems
Looks at the many types of launch vehicles and propulsion technologies that are in service or proposed.
http://www.hobbyspace.com/Links/LaunchPropulsion.html

Ship Propulsion Equipment Directory
Propulsion, Transmission and Engine Room Equipment - Equipment and Services
http://www.ship-technology.com/contractors/propulsion/index.html

How Electromagnetic Propulsion Will Work
Get a sneak peek (even before NASA scientists) at a new type of spacecraft that could be jolted through space by electromagnets.
http://www.howstuffworks.com/electromagnetic-propulsion.htm