Re:Working out with injuries
Having suffered from tendonitis, I would seriously suggest you check with your doctor before following the advice above. It doesn't sound appropriate to me. The medicine ball will still add a significant amount of resistence to your shoulder (perhaps more than light weights). And, I find holding the ball to be more aggravating than holding free weights.
My suggestions (in addition to Talking to Your Doctor) are pure cardio dvds (skipping any bothersome large-arm-movements). I personally enjoy dance dvds, anything by Jen Galardi tends to be fun and well-cued. Remember: you can skip arm movements if you feel you'd like. Would you like to try some barre work? It tends to focus on the lower body; element ballet comes to mind. You might want to consider pilates, but beware than many pilates dvd include several plank positions which might be bothersome; so I immagine some might be poor choices (perhaps someone has a specific suggestion?)
Your doctor, of course, and your own instincts, will be good advisors.
Hope you heal quickly!
"Every man's life is a fairy tale written by God's fingers." ~Hans Christian Anderson