
Total weight: a few ounces. Space in your suitcase: negligible. Effectiveness: huge.
Granted, it will take some practice and a few good size welts on your back before you become proficient at it. However, once you get the hang of it, you can use it in any area that has a relatively high ceiling.
Start by just trying to get 20 jumps in a row, and keep doing sets of 20 for 5 minutes. Try increasing your reps before stopping by 5 and add a minute on each successive workout. Before long, you will be able to get a killer cardio workout in 20 minutes no matter where you are.
At times, going for the simple and basic approach is the easiest way to get something done. It also cuts down on the excuses you have to miss a workout.