Balancing your forearms on a ball is an amazing workout for your core. The variation shown below involves placing your palms on the ball, standing with your feet wide, and your hips over your ankles. Then lean forward, allowing the ball to roll underneath your forearms. Use your core and legs to bring the ball back to the starting position. Complete three sets of 10 to 12 reps. For a more challenging variation, check out this video demonstrating the circling plank. Complete three sets.
This fun move not only works your core, but will also tone your inner thighs. Lie on your back holding an exercise ball above your chest, extending your feet up toward the ceiling. On an exhale, move your arms and legs away from each other, lowering both toward the ground. Inhale to bring them back toward each other, and transfer the ball from your hands to your legs. Then lower your arms and legs toward the floor away from each other. Bring them back together, transferring the ball back to your hands. Continue like this, completing 10 to 20 reps. Here's a video of this move in action.
Get an amazing stretch for your back and abs while also strengthening your core. Lie on your back on a ball in Wheel Pose with your feet and hands resting on the floor. Hold here for 30 seconds or so, just stretching the muscles in your back and abs. Then as you inhale, shift weight forward toward your feet and use your abs to lift your torso up. Reach your arms out in front of you. As you exhale, very slowly lower your spine back onto the ball and come into a backbend. This counts as one rep. Complete three sets of 10 to 12 reps.