• some electronics projects → http://www.electronic-projects.net
• video → http://www.epanorama.net/links/videocircuits.html
• the analog aproach → http://arraydesign.com/downloads/index.html

gEDA is “a full GPL'd suite of Electronic Design Automation tools. These tools are used for electrical circuit design, schematic capture, simulation, prototyping, and production. ” » http://www.geda.seul.org/

• http://octopart.com
• http://mercateo.com
• http://componentsearch.com