Marketplace for the electronic engineering industry,
http://www.electronicsweb.com/
From timers and oscillators to RF transmitters and amplifiers. Simple and fun circuits to build.
http://www.uoguelph.ca/~antoon/circ/circuits.htm
Services on carrying out R&D relating to millimeter wave radar technology, including all weather, day and night operation radar sights, fire control radars and armoured vehicles based command and control systems.
http://lreri.tripod.com/services.html
Site includes over 100 circuit diagrams, links to related sites, commercial kits and projects, newsgroups and educational areas.
http://ourworld.compuserve.com/homepages/Bill_Bowden/homepage.htm#menu
Links to information and resources dealing with mechatronics including actuators, sensors, microcontrollers, and motion controllers, products, books and references, conferences and proceedings, and journals.
http://www.engr.colostate.edu/~dga/mechatronics/resources.html
Includes definition of terms and links to categorized resources.
http://www.links999.net/robotics/
A variety of free electronic projects that you can build. Quite a few circuits with theory of operation, and parts lists. Excellent reference site.
http://www.electro-tech-online.com/viewforum.php?f=7
Online locator and exchange service for semiconductors and IC's.
http://www.onlinetechx.com