The Transmission Rebuilders Network  
   World-class transmission rebuilders from around the world interacting on transmission diagnostics and repair.
   http://www.transbuilder.com/

Aamco Transmission Centers  
   Fixing manual, or automatic transmissions.
   http://www.aamcotransmissions.com/

Understanding Automatic Transmissions  
   What to do when your automatic transmission does not work, or if it does work, how to keep it working. Also, a description of engine and transmission theory.
   http://www.automatictransmissions.net

Pre 1929 Vintage Chevrolet Transmissions  
   Provides instructions for teardown, inspection, repair and assembly of Pre WW-II Chevrolet Transmissions. Lists replacement part numbers, information on Johnson Overdrive and a source page listing over 30 dealers for all types of Chevrolet related items.
   http://www.cybersurfers.net/~herb/gearbox.htm

A Short Course on Automatic Transmissions  
   Long article explaining the concepts behind modern automatic transmissions and their repair.
   http://www.familycar.com/transmission.htm