I bet every girl in the world has.
The quickest and easiest "way out" is the classic "loose bun", also called "chignon".
To realize this hairstyle you need to remember that your hair shouldn't be completely clean, because smooth hair are harder to catch in a bun. Brush your hair from the top to the end; after that you have to decide what kind of bun you want: if you prefer a "messy" one you don't have to apply any hair gel or hair spray, whereas if you want to obtain a more classic and elegant hairstyle you'll need to apply those products.
Grab you hair and apply a hairband about in the middle, bottom, top, or side. Wrap the hairband twice to make sure it is tight. Wrap the same hairband again but stop halfway. Fix it with some hairclip and if you want you can add an accessory to decorate your bun (i.e. alicebands, ribbons, etc).
This look is a trend for this Spring/Summer 2012 because it gives you a "messy allure" which is both cute and stylish.
A more complicated version of the classic bun is the following one.
There is also an alternative kind of bun: the so called bird nest bun, which consists in a high back- combed bun which is perfect for elegant occasions.