Men's Health is the perfect place to get workout advice for toning your abs. The "medicine ball chop" exercise will work all of your muscles as you rotate and move through the full range of movement, giving a great abs workout.
Stand holding a medicine ball with your arms straight, and over your left shoulder. Pivot to the left so your right heel rises off the floor and your torso faces left. This is the starting position.
Quickly bend your knees and rotate your torso to the right as you draw your arms across your body and down. Once the ball is outside your right lower leg, quickly reverse the motion to return to the starting position. Complete your reps then switch positions to work the opposite side. Start off slowly before building up speed. You should always be in control as you accelerate and decelerate from top to bottom and back up.
This exercise will work muscles from the fingers to the toes as you rotate and move through the full range of movement.