From Fitness Attitudes:
Cardio exercise intensity can easily be varied through speed, incline, distance, height, etc. And of course the types of exercises are practically endless, so exercisers should never have the excuse that theyve exhausted their exercise options. Good cardio examples include: walking, jogging, swimming, biking, hiking, and more. In addition, combining several of these exercises into one workout session can be very effective. Try 10 minutes each of 3-4 unique exercises. This version is the first release on CNET Download.com.