Geoff Waterson's TR606 Modifications
Some very cool mods for the TR606 that translate fairly easily to the CR8000. My bass drum decay mod is similar to Waterson's 606 bass drum decay mod.

SynthDIY.com
A deep resource for TR606 mods and a heck of a lot more. The TR606 and CR8000 have similar voice circuits, so if you're wanting to mod your CR, a look at all the 606 mods is a good place to start.

Estecho
A great site full of vintage drum machines and some brilliant tips. This is where I got the idea to flip the 1/4" jacks on the rear panel for use as individual outputs.

FutureKomp Records
My favorite netlabel, where the music is free but the robots aren't.

Small Bear Electronics
My usual source for pots, micro-mini switches, and knobs.