back in hs football, coach used to make us do what he called saigon squats....
basically a very wide stance squat to the middle, and then leaning to each side.....i still do these when my hips are tight, and between sets of squats and after squats....
i also get in a lunge postion and get a good stretch that way as well....
box squats really hit the hips, and lately my hips have been noticably sore and tight.