Simplify your wiring: You can get 'ribbon wire' is various gauges and numbers of wires. One example would be the wiring used on trailers...all together until you need to run a lead to a component.

ALSO:

Check out www.painless.com for wiring components like gang plugs. These will allow you to break your wiring into segments for easier installatino/removal of electrical components. Your car probably has come crude gang plugs where the headlight wiring hooks into the main wiring harness on the inner left fender liner.

I've been 'window shopping' in the kids' section of auto parts stores. I see they have shifter knobs with up to 4 buttons, and they're wireless! You can hook up your OD, driving lights, etc. to the shifter knob without running any new wiring. Pretty cool!