I notice that when I do static stretching in my legs/hips, I lose a lot of power squatting and cleaning. Deadlifts too, but I'm starting to phase deadlifts out of my routine.
I'm going to try warming up with the foam roller today. Lately I've been stretching my upper body with the barbell, a short upper body routine I stole from a Chinese oly lifting video. But it doesn't really open anything up for benching or even pulling.