We had a brazilian Miss Universe staying with us for a few days and she has a mega butt.
She does lots of stretching to keep the fascia around the glutes free and lots of lunges, deep half squats, stiff leg deadlifts, lying face down reverse leg raises with 20kg ankle weights!
Check this link for one of the finest butts I've ever touched, er no sorry, SEEN.
http://www.veoh.com/videoDetails.html?v=e106753574t6aNa www.extremenutrition.co.uk