Amazon MP3 Store is celebrating their fifth birthday by giving you a credit that will allow you to purchase a $1.29 song for just a nickel for limited time. To get this deal, all you have to do is let your Facebook friends know what your favorite song is. A credit will be automatically added to your account and the next time you purchase a $1.29 song you will be only charged 5-cents. Deal expires October 10, 2012.