Step 1: Make the Hangers
Grab some rope or cord. Pictured below is approximately 1/4 inch 'clothesline'. Like a lot of my instructables, I used what I already had. Cut the rope into approximately 2 foot long pieces. Melt the ends if you so desire. Now tie each piece of rope into a loop. Use whatever knot you like. I think I used a simple overhand knot. Hold both cut ends in one hand, make a loop, pull the ends through the loop and pull it tight.
Step 2: Use the Hangers
Coil up your cord using your favorite method (hmm... maybe another instructable?). I like to plug the ends of a single cord together for some reason. Maybe my dad does it that way, maybe granddad?
Once you're all coiled up, pass the hanger through the coil. Then, pass one end of the hanger through the other end. Hang it up by the end you just passed through the other end.
Another reason this is nice is that you can hang a bunch of cords off of a single 16d nail.
You're done. Now when you need an extension cord, pull it off the nail, undo the hanger, plug stuff in and make noise!
This method also works well for ropes, hoses and other long skinny coiled things.