Don't have time to get to the gym? Scratch that excuse! You can exercise at home. If you're only going to purchase one exercise item, buy a balance ball. Gaiam's Total Body BalanceBall Kit ($25; gaiam.com) includes a workout DVD, an exercise band, and a burst-resistant ball. Ball exercises are easy on your back but strengthen your core muscles -- which you'll need for labor. Plus, readers tell us that holding a baby and rocking gently on a ball does wonders for soothing a crying baby, so you can use it postpartum also.