Foam rolling is an excellent form of recovery post workout. It is a form of stretching (just like you'd do normally after a workout), and gets tightness and knots out of muscles that have been worked out, or are just generally tight. Like a good massage, it can really HURT, but in a good way, and when you finish you feel instantly looser and more aligned. It releases knots and tightness by rolling over the muscle, and in a way, stretching it out, and forcing it out. (Think about a rolling pin rolling some dough).
You can stretch most muscles with the foam roller, but the best I've found are the back, glutes and legs. My quads, calves, glutes and hamstrings get EXTREMELY tight because of all the exercise I do, and I sometimes get knee or hip tightness/pain as a result. I find after a quick foam rolling session, this pain lessens dramatically.
Your IT band runs down the outside of each thigh from your hip to your knee. You probably won't feel the tightness there until you get the right pressure on it, but when it is loosened, it feels AMAZING.