Here is a cardio routine I used when I was in college.  It gave me some great results, while greatly improving my endurance and speed during my weightlifting sessions.  This cardio routine is quite an intense workout, and I would not recommend it to anyone who is not in decent physical shape.  It combines interval training with plyometrics for the ultimate calorie incineration.

Here’s the workout:

• Intervals on treadmill @ 5 incline for 20 minutes
  • 30 seconds sprinting at max speed (~8-10mph)
  • 30 seconds brisk walking at 4mph
• Jack/Jump
  • alternate Jumping Jacks and Jumping Rope for 2 mins each for 16 minutes
• Jump Squats
  • 25 reps x 5 sets with 30 second rest between

By the time you are done with this workout, I guarantee you will be wasted.  If you are still not tired, try increasing the intervals to 30 mins.  This routine will burn a ton of calories, and get you in great shape.