That Hydra of power and USB cords at the back of your desk isn't going to un-knot itself. But if you don't want a freestanding box to organize your accessories, Cordlets may be the answer.
Cordlets are a minimalist means of keeping your desktop tangle-free. Just stick them to any flat surface, slide a the cord from USB device or your mouse through the gripping channels, wrap the excess around the base and boom - you've got instant tidy. They come in both white and charcoal and are available from Quirky, $10 for a 4-pack [via Quirky]