Here's a quick cardio program for you.
You can use this on a machine like the treadmill, or out running.
Warm up 5 min
Exercise hard (level 9 or 10) for 45 seconds
Follow this with active rest for 45 sec (level 3)
Repeat for 6 intervals
Finish with 5 min cool down at level 3
That's it! It really works.
You can check out this post for a video sample of this type of workout.