Ah, the BOSU... This little known piece of equipment can become your new best friend with a little research and practice. Swiss balls for abs have been the rage for the last few years, but the BOSU goes one better. The name stands for Both Sides Up and I absolutely refuse to lend mine out : ) It's basically half of a swiss ball, attached to a solid platform. You can put the solid side down and use the ball side for your ab exercises, step aerobics, balance exercises and involve your core muscles for balance when performing pushups, planks etc. With the ball side down, your core muscles go into overdrive when you perform pushups on the solid side. The added benefit here is that you can tilt your platform to any direction before begining your pushup to put extra emphasis on muscles where you need it. They retail for around $90 but check your local gym's group fitness classes to see if they have any. Slowly but surely they're catching on. Try it out and tell me you don't love it : )