Electronics Related

Makers, Hardware Hackers, and Repositories of Awesome
ladyada.net - LadyAda has a lot of nifty stuff on her site, as well as a far superior list of links and resources.
hackaday.com - A hack a day keeps the madness away.
Make Magazine - An actual print magazine devoted to making cool stuff. Worthy of paid subscription.
Sam Barros' PowerLabs - All kinds of life-threatening fun!
Afrotech Mods - Squirrels, chaos, and electronics in some amusing unholy union.

Datasheets and circuit ideas
datasheetarchive.com - Free repository of millions of data sheets
datasheets.org.uk - Appears to be a clone or partner of the above
datasheet.in - another clone site
datasheet4u.com
A list of datasheet sources, much more extensive than mine

Manufacturers
Zilog - makers of the Z80 microprocessor
Microchip Technology - makers of the popular PIC microcontrollers
Atmel - another microcontroller manufacturer, these folk make the AVR chips
National Semiconductor
Maxim
Texas Instruments

Distributors / Retail
Mouser Electronics
Digikey
Electronic Goldmine - a great surplus supplier
All Electronics - another surplus merchant

Science

Physlink - keeps track of cool developments in physics
JPL - Jet Propulsion Laboratory

Reference

Wikipedia - An online encyclopedia without equal.

My old sites which I have abandoned

Pearls Interface - An aborted attempt at a cryptic web portal. Looks kind of neat.
SimmoralTech TI-86 - My TI-86 assembly programming site I had in highschool. It got me hooked on programming, so I keep it around. (Actually, the real reason is that I lost my user/passw, so I can't access it anymore :)