Swimming:
What is great about swimming is it has no impact on your joint, but what we are talking about here is serious swimming like doing some laps in a pool, when swimming, you will burn a great amount of calories and still enjoy the cooling effect of water.
Jogging:
Start with a pace you can keep up with for a longer distance, if you can't then start with fast walking, Jogging has a great effect on your strength and stamina and burn a lot of calories.
Stair climbing:
Do it any where at home or after work it is an effective way to burn calories, you can maximize the effect by jumping one step with both legs together or two steps at a time, but watch out you may injure your self.
Jumping rope:
A great workout that don't need much space, you can do it in your bed room, It has a powerful effect burning calories and circulating the blood all over the body, and can be turned into contest with friend for who can jump for a longer period of time.
Running:
A bit harder than jogging and but its worth the effort just keep your speed at 8 mph or higher, Running with friends or while listening to music can help you ran longer distance and be a motive to beat your own records.