What are some good exercises to help tighten a post-pregnancy tummy?

I had my daughter nearly three weeks ago and have already shed all but 5 pounds of my pregnancy weight. Now I want to start tightening up this loose skin and muscle. What are some good exercises to tighten the upper and lower abdomen that won't strain my back too much?

Exercise ball crunches - This is a good one if you are just starting to exercise.- Step 1 - Sit on the ball and place your hands on the back of your head and walk your legs out lowering your body on to the ball until your upper back and shoulders are all that remain on top of the ball. Legs should be shoulder width apart.- Step 2 - Lift your pelvic to straighten your lower back and tighten your buttocks and contract the abdomen muscles.- Steps 3 - Keeping your elbows pointing out to the side slowly raise the shoulders slightly being careful not to pull the neck. You should feel the crunch in the abdominals; the thighs and buttock muscles will be working too.- Step 4 - Hold the position for a moment then slowly lower the shoulders to the ball and repeat for as many times as you can perform the exercise without straining.Rest for 30 seconds or less between sets. Do 2 or 3 sets of 12 to 15 repetitions every other day.Floor bicycle movement – This exercise does not require any equipment.- Step 1 - Lie on your back with your hands behind your head and legs straight out.- Step 2 - Contract your abdomen muscles and lift one leg bending your knee while raising your shoulders slightly off the floor without pulling your neck.- Step 3 - Bring your elbow and knee together bending so that the elbow and knee just touch.- Step 4 - Lower and then change sides so the alternate legs in a bicycle movement touching knee to elbow. Repeat .Move through the positions slowly. You can vary this ab exercise by bringing the knee and elbow of the opposite sides together requiring the upper body to turn slightly from side to side. This maneuver is very effective and works the oblique as well as both the upper and lower abdominals.Hanging Knee Raises – This is a most effective exercise but needs gym equipment (Captain’s Chair. )- Step 1 - The body is held upright by the arms resting on padded arm bars with the feet handing down. The lower back is straight and supported by a back rest.- Step 2 - Contract the abdominal muscles and lift both knees slowly up toward the chest,- Step 3 - Pause and then slowly lower the legs back down to the starting position. The muscles are constantly contracted throughout the exercise.This abdominal workout is the most effective because it works both the upper and lower abs, back and arm muscles for an overall core strengthening exercise.The Best ResultsIt's not enough to just focus on doing abdominal exercise. For women especially, - you can have rock hard abdominal muscles, but if there is body fat covering them you won’t be able to see them. To make these exercises not only pay off but really show off you need to consider the following;- Eating a well balanced diet low in saturated fats- Doing a cardio or Aerobic warm-up before a workout- Stretching both before and after exercise for increased flexibility- Making regular exercise part of your lifestyleConclusionOther ideas: