• 4QD's pages of interesting circuits
• Aaron's Electronic Circuits - descriptions and circuit schematics
• AirBorn Electronics Circuit Design Library - microcontroller circuits
• American Electromechanical - RF module, wireless control, and video switcher
• Andy's PIC Project Page
• Bob's Music/Audio Electronics page
• Bowden's Hobby Circuits - a nice collection of various circuits
• Brett Bymaster's Circuit and Software
• Broadcast-Quality FM Transmitter Designs Index
• Circuit Cellar Home Page
• Circuit from Forrest Cook
• Circuit Lab - an assortment of circuits
• Circuits Library - an excellent collection of circuits and data sheets
• Circuitland - hobby electronics circuits
• CyberCircuit - Free circuits as well as two CD's containing over 1100 circuits for reference (requires $$)
• Diana's Electronics Info and Circuits - Good beginner information and circuits
• Dib's Circuit Collection
• Digital Music Zone - Music related circuits
• Electrical Engineering Circuits Archive - the "one-stop" electrical engineering information source
• Electronic Cookbook Archive - very good archive
• Electronic Rainbow Inc.
• Guitar Amps
• HAM radio circuits at nic.funet.fi - some circuit for radio amateurs
• Hardware Web - Midi hardware projects page
• Jerry's electronic plans, kits, and curious things
• Ken's Railroad Electronics Page
• Low-Cost Electronic Projects By Fred B.
• Mark Sokos' Electronic Circuits
• Mendoza's Electronic Circuits
• Model Railroad Electronic Circuits
• Music Electronics Archive
• Nostalgia AirVintage Radio References
• PAiA: Touch Switches
• Radio World - Radio Info for the UK
• Robotics Circuit Schematics
• Tomi Engdahl's electronics
• WE-MAN's Electro stuff - many circuits and documents
• Wenzel Associates Technical Library - Time and frequency circuits as well as several other good resources

Novasoft Mekatronix - Autonomous Robots, Support Software, Microcontroller Printed Circuit Boards, Servos/Gearhead DC Motors, Sensors

Precision Navigation, Inc. - Electronic navigation modules and more!

Wirz Electronics - A good source for odd components (sonar, Nitinol wire, robotics, etc)

Zorin Microcontroller Products

Online Electronic Educational Resources

Designing Amplifiers Part 1, 2, 3, 4, and 5 - By Richard Lloyd Measures

Wenzel Associates Technical Library - Tutorial and Reference Articles