If you have access to two medicine balls and have a partner, I've got a pretty fun routine for you. Abs can be quite boring, not as bad as cardio, and this makes it fun.
Set up on an incline bench as you would for sit-ups. Have a partner on the end by your feet. Have a ball in your hand and have your partner grab the other ball.
With the ball in your hands, do a sit-up. As you sit up, throw the ball low by your partner's groin and at the same time, have your partner throw the ball high so it goes over the ball you just tossed to him.
You both catch the balls and then you do another sit-up. Then you toss the ball low as he tosses the ball high. Catch and do another sit-up. Repeat. So the ball kind of looks like a sideways juggle. It's kind of fun because you both have to be coordinated together. If he's not watching, the ball could hit him in the nuts. And sometimes, if you've exhausted yourself, you can't sit up and the ball still comes raining down on you.
The second exercise is sort of a medicine ball crunch. Sit on a mat or pad and get on your back. Lift your legs as if in a crunch position but without the bench. Have your partner from about waist high drop the ball on your abs as you tighten up your abs and get hit with the ball. Exhale like a boxer as you get hit with the ball. Then grab the ball and put it on top of your shins and instep, kind of balancing it there. Then your partner grabs it and again drops it on your abs. You kind of do a weighted crunch and also do some impact work at the same time. Repeat each exercise for about 20 reps each for 3 sets and that should be plenty. Then diet, cardio and then shave hair off of new six-pack in about 8 weeks.