Air Breathing Propulsion

Rocket Propulsion

Gas Turbines

Liquid

Large Commercial

F-1

Small Commercial 

H-1

Military 

J-2

Advanced Concepts

Hybrid

Ramjets / Scramjets

Solid 

Pulse Engines

Micro 

Micro Engines

Electric

Nuclear

Space Propulsion

Historical

Electric (cross link)

Nuclear (cross link)

Micro (cross link)

Chemical Rockets (cross link)

Solar/Thermal

Advanced Concepts

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Useful links:

http://www.aircraftenginedesign.com/enginepics.html

http://www.aoxj32.dsl.pipex.com/

http://grin.hq.nasa.gov/subject-space.html