This exercise is great for your shoulders. To perform it you will only need an elastic band.
Wrap an elastic band around a door knob or something stationary. Hold the band with your opposite hand. Elbow is forming 90 degree angle and is tight into your body.
Rotate your arm so that your palm is facing front. After repeating this movement several times, switch arms.
Exhale as you rotate your arm to front, and inhale as you return it to starting position.