This stretch is great for your chest area (the pectoralis muscles). In this photo I use an exercise ball, but you can use a wall or the best place is a door way. As you hold onto the doorframe you can lightly press into it towards you as your body is slightly forcing itself away from the arm. Also, in a doorframe, you can bring your hand up or down to feel the stretch in different areas.
Stand side to side with the door or kneel by the ball. Place your hand at the same height as the shoulder (you can shift levels to target an area). Shift your body (or roll the ball back) so that you are facing away from the ball or door frame (see above).