I don't have a pic or a cord handy to take a pic, but I'll try to describe. You may have seen this on service trucks running around town.
First, I usually do this on 100' cords, 50' minimum. I double the cord over on itself, essentially 'folding' the cord in half, ie. 100' cord doubled over is now a 50' length. I go to the looped end, middle of the cord, and loop it over on itself, making a knot with a loop about 6" in diameter. You reach thru the loop with your hand and pull the pair of cords thru about 6". So you have a pair of cords thru the loop and have made another loop. You reach thru this loop and grab the pair of cords again and do the same. You do this until you run out of cord, you've made a big multiple slip knot. When you grab the plug ends, you keep pulling and it undoes itself until you get to the loop you made in the middle of the cord. A drawback is that it makes the cord look like a stretched out coiled phone cord when it's laying on the ground, and you should always use a cord at it's full length, not coiled up, it's tempting to just undo what you need. But once it's braided, it folds up nice and flat on itself and stores easily. It's a little work, but far less work than untangling a rolled up cord done using your arm and elbow.
