High intensity interval training (HIIT) is one of my favorite ways to do cardio. Basically it involves short periods of maximum exercise followed by rest/recovery periods. It has been shown to improve performance and burn more fat than traditional cardio sessions. You can do this interval training on any machine at the gym or running outside.
Here is a sample HIIT session:
1. Run for 2 minutes at a level from 3 to 5
2. Run for 1 minute at a level of 6
3. Run for 1 minute at a level of 7
4. Run for 1 minute at a level of 8
5. Run for 1 minute at a level of 9
6. Repeat numbers 2 through 5, 3 more times
7. Run for 1 minute at a level of 10
8. Cool down for 2 minutes