Kudos to my wife for this great tip! We both own MacBook Airs, but I primarily use mine at a docking station at work while she takes her's EVERYWHERE. After two years of constantly wrapping and unwrapping the cord from around her power adapter it finally stopped charging. Turns out the junction where the cord enters the power adapter/brick had been crimped to many times and the wires within the cord had broken. So she bought a new power adapter and devised a way to wrap the cord around the power adapter in such a way as to not crimp the cord and therefore extend the life of your quite costly power adapter! Pass this tip along to anyone you know with a MacBook (Pro or Air, they both use the same type of adapter brick)...they will thank you for it.
Before you start wrapping the cord around the power adapter make a small loop (just like when you 1st learned to tie your shoe) like this:
Then wind the cord around the power brick just as you normally do. You end up with a neatly wound MacBook power adapter without crimping the cord!