I know two really intense workouts that'll get you really cut, but when I say "really intense" - I mean it.
Swimming style -
Swim 3-5 laps (or however many you get in about 5 minutes, an above moderate pace. You can do freestyle, or alternate strokes - personally I like to alternate strokes).
Immediately get out of the water and do 35 pushups and 35situps, then immediately dive back into the pool and swim another 3-5 laps. Repeat this process for as long as you can, I generally do about 45min-1hr per cycle.
You should get AT LEAST 3.
-Run for .5 miles at 5min-6:30min pace, or run 1mile at a 6:30-8min pace.
Then immediately do 35pushups, 35situps, 20dips, and 10-15 pullups.
Rinse and repeat this for about an hour. The rule of thumb is to get at least 3 sets of each accomplished, and work your way up towards eventually being able to do 10. It'll get you cut and in incredible cardiovascular shape.