Headphones can unravel quickly in a bag or pocket. If you're looking for a dead simple way to keep them tangle-free, Instructables user timwikander suggests stuffing them in a chapstick cap.
We've mentioned you can do the same thing with a binder clip before, but this method is handy if you don't happen to have a binder clip around. You simply wrap the cord around your hand, then stuff it into the cap to keep the cord from untangling. This will only work with earbuds, but if you have some spare caps around, it's not a bad way to keep them organised.