Almost everyone has skipped rope at some time in his or her life, but other than boxers, most of us left it on the elementary school playground. Fact is, skipping rope isn't just beneficial to the cardiovascular (CV) system. Skipping rope for 15 to 20 minutes a day is practically unrivaled as a total body workout. Not only is it a good CV workout, but it improves your agility, fluidity, coordination, lateral movement, explosiveness, speed, and timing. While you cannot really increase your muscles, size by jumping rope, you can (and will) increase the muscles efficiency, and because of this, many coaches employ it as a means to complement strength or weight training.
Boxers are some of the fittest athletes on the planet and skipping rope is their staple exercise. It is no wonder: Boxers need full-body fitness and coordination, and no one other exercise develops this as well. While it obviously works out the legs, it also tones the entire upper torso - chest, back, shoulders, triceps, biceps, and forearms. It is also a fine exercise for developing lean, cut muscles - ever had a look at Oscar De La Hoya?
The other nice thing is that you need neither much space nor equipment to exercise. Jump ropes range from around $3 to $15 dollars and, as already mentioned, you can do it in as little space as a prison cell. Nor is it difficult to learn. Refining your skill until you're reminiscent of Muhammad Ali (crossing your arms, making double and triple jumps, etc.) make take some time, but most of you will be able to go until exhaustion on your first day, although I would not recommend doing so.
If you have no experience at all jumping rope, I would recommend buying a how-to book or searching the net for technique tips. While this would most likely be time-efficient for your learning curve, you can also just jump right in, so to speak. Like starting any exercise, start slow. Do only 100 repetitions on your first day, perhaps doubling that on day two (with a rest day in-between each workout), then again on day three. This may seem absurdly light but the alternative is doing too much too soon and risking becoming so sore that you can hardly walk. With exercises that are technically fairly easy, it is beneficial to impose some restraint when starting out, even if it feels as though you can do much more. Don't be too impatient. Your calves adapt quickly and many people will be doing 10-minute sets within a couple of weeks.