Best ways to do cardio other than running?

Any activity that elevates your heart rate for a sustained period of time can be a good form of cardiovascular exercise. Things like swimming, cycling, walking, skipping with a rope. It can even be other cross training activities such as boxing, aerobics - anything that you find interesting and enjoy. To keep your training interesting you could do a mixture of different activities. I guess it depends on what you are training for too. If you are training for a specific sport, you might be able to find something that compliments your sports-specific training. If you are training just for the sake of general fitness, then it doesn't matter too much.