Dan Stahlke's web page

commandlinefu.com
If you use the Unix command line, this is definitely worth checking out
Bill Beaty's Science Hobbyist
Lots of amateur science stuff
AVR Freaks
The availability of this resource was the reason I got back into microcontrollers
Techlib
Information on home-made VLF/ELF receivers
Electric Field Disturbance Monitor
This circuit can detect movement from across the room by monitoring changes in the ambient electric field
I want sparks & I want them NOW!
Simple high-voltage Marx generators

perl -e 'print "P1\n256 256\n", map {$_&($_>>8)&&1} (0..0xffff)' | display