Why not add a new dimension to your workouts with Gym balls. These large inflatable balls are a great fitness accessory that can be used for all types of exercises and physical therapy. You can sit on them, throw them, catch them, balance on them, whatever you want to do.
Gym balls make your workouts more challenging by producing an instability that your body has to work against. When doing exercises on a gym ball you are made to engage your core muscles to keep you balanced and therefore they are forced to become stronger.