The gym I used to go to had the best class called "Bosu Bootcamp". It was so great--a mixture of cardio using the Bosu (a lot like step aerobics but on the unstable surface...great for the core!) and then bootcamp drills like pushups using the bosu's flat side ("BOSU" stands for "BOth Sides Utilized" so if it's a good class it should use both sides of the bosu for some killer drills), plyo moves, etc. It's also great to lay on to work your abs or stand/lay on to do upper body work.