Fitness.com is an awesome site with fantastic exercises to mix up your routine. This exercise is definitely advanced but worth the time and energy. Advanced exercises can be very hard to find on the internet so save this one in a file or print this article out (see the links below the article). The stability ball challenges your core, while the medicine ball adds weight to your upper body to challenge your shoulders and increase the intensity of the ball exercise.
Check out this great exercise at Fitness.com