Eagle library for USB connectors printed directly on PCB.
A wiki of designs, schematics, and links to open source electronics projects. If you get lost in here long enough you'll find some interesting stuff.
Fritzing is an open-source graphical application for converting a project prototyped with an Arduino into a PCB schematic for manufacture. Designed for people already familiar with Processing to do what they need to do easily. Cross platform: runs on Windows, OSX, and Linux.
A website which lets you design circuitry online in your web browser (i.e., without having to (buy, download and install PCB engineering software). The online circuit designer contains a library of known, documented, and trusted subassemblies of circuits (like power supplies, amplifiers, and volume controls) that you can use as the framework of your circuit, but you have to add the rest. They plan on making it possible to automatically generate and e-mail all of the files a third party small-run manufacturer would need to etch, drill, and mail your circuit boards to you.
3750 links, including 200 private