A good way to pass the time is to put you in a zone. In this zone you will not even realize that you are working out. You just keep on going because your mind is totally focused on something other than how much more you have until your cardio session is over. Aerobics classes are a good example of this because you have more than one movement over and over. Also the music in the classes seem to dull the pain.
Music is so very important in getting into a zone.
We all know that people have different taste in music, so it might be a good idea to get oneself a portable walkman of some kind. This way you can listen to the music that gets you going in your environment. Try not to dread cardio, but embrace its' importance. You might find that you have a different view of the activity. It is all a part of your total body experience, so train your mind and your heart will thank you.