A coiled cord is wire-wrangling perfection. It stays compact and lean where you want it to, but suprises you with its stretch and range to reach across a room when necessary. If you want to turn existing cords into coiled ones, Make: Projects has easy-to-understand instructions on coiling cords the safe way.
You'll need a few semi-pro tools, like a heat gun and a mutlimeter, to get this project done. But if you know what you're doing (or have a friend who does), being able to coil your own cords around the house is an invaluable tool towards cord control nirvana.
It all starts with wrapping your cord around a metal tube (called a mandrel) and setting it in place with heat from the heat gun. It's a simple process, sure, but it's easy to make a mistake and damage your cord for good. If you're going to tackle this project, make sure you follow the insturctions at Make: Projects "to a T."
Or Try a Chain Sinnet...
Want a simpler solution for "shortening" long cords? Try a chain sinnet. You don't need any tools (other than your hands) and it's nearly impossible to mess up! Check it out here: Keep Extra Long Cords in Check with a Chain Sinnet
(Images: makeprojects.com)
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Better idea: Roll up that nice long cord and put it away until you need it. Then go out and buy a shorter one... that way you get a shorter cord, but don't need to ruin one to get it.
Also, coiled cables are annoying - that tiny amp in the picture will get pulled off the table as soon as the guitarist reaches for something that's more than a meter away... and don't even get me started on coiled headphone cables that only attach to one side - if I wanted to walk lopsided after an hour of head phone use, I'd just hit myself in the knee with a baseball bat :p
Beware that your result will vary. Some cords will not hold the coiled shape, no matter how much you heat them. Also note that coiled cords are more sensitive to white "noise".