My coach gave me hard foam roller to "roll out" the muscles of my hip and i-band when it feels tight. It works! It's about six inches in diameter and pretty solid. I'm not sure what its called but I will find out when he gets back in town.

There are also some stretches that help the hip and surrounding area, including the glutes. If your left leg is the one that's tight, sit on the floor with your knees bent in front of you. Bring your left knee down so the outside is flat to the ground. Your ankle should be flat also, and the knee joint should be bent around 90° in front of you. Extend your right leg straight behind you. You may have to hoist up with your hands to do this. When your leg is behind you, slowly lower yourself down in a sitting position. Now lean your upper body foward. You can really start to feel the stretch in your hips and glutes. Adjust your knee angle/lean direction until you stretch exactly where you need it.

Another stretch I do is specifically for the i-band. Put your left hand on a desk or high bed. Bend your knees a bit, then extend your left leg behind you and as far past your right knee as possible. You should be moving your left leg laterally, not backwards. Keep the left leg straight, taut and the side of the foot against the floor. Slowly lower your body by bending your right knee and your left elbow. As you lower, your left foot will slide out farther. You will feel the pull of your iband as you do this.

Do both of these enough to stretch, but not to the point where you feel knee pain. Hope this helps!