A mini trampoline, also known as a rebounder or trampette, may not be the first piece of useful home exercise that comes to mind, but the fact is they are very effective, fun to use, and cheap to boot. It's the rare person who will do an entire 30-45 minute workout on a rebounder, but vigorous jumping will really get your heart rate up quickly, so one of our reviewers starts with 10 minutes or so on the trampoline, then transitions to a different workout already in the optimum fat-burning zone. Or, if you have just a few spare minutes, you can hop on one to quickly get your heart pumping, which is better than nothing. Diet guru Gillian McKeith swears by trampettes as a way to fit bits of exercise in during the day and relieve tension. There is also a widely cited NASA quote that the mini trampoline is "one of the most efficient and effective exercises yet devised by man"--that sounds a bit over the top to us, but there's no denying this simple device can help many people lose weight and have fun while they're doing it.
Mini trampolines are relatively low impact, but you'll want to consult your doctor if you have joint problems and such. This sort of aerobic jumping can improve balance, coordination, and most importantly, burn quite a few calories. There are variations other than a simple jump--going from one foot to the other for instance, raising knee, moving arms, etc., and a good trampette will have a manual describing these variations or sometimes a DVD showing them. Again, most people won't use this for their entire workout, as boredom will set in around the 5-15 minute mark, but it's great to be able to hop on for a few minutes, and a bit of bouncing can really liven up the monotony of a different type of workout.
There are various shapes and sizes available for mini trampolines, but we think a round 40-inch diameter model is ideal, 36 inches being just that bit too small and anything larger simply taking up too much space unnecessarily. They are universally easy to put together (unlike large trampolines, as our reviewers known from personal experience). Just put it in the corner of the lounge and you can bounce while watching the telly. You do need to look out for your floors though--you'll wear a dent in carpets and possibly even mark wood floors, so a small, cheap rug or somesuch underneath is a good idea.
We found the Bodymax Mini Trampoline the best mix of value and quality manufacture, though you can spend as little as a tenner on a flimsy one or as much as 80 quid on a high end model if you're so inclined.
Prices: The Bodymax Mini Trampoline DVD retails for £39, but you can get it much cheaper on Amazon for around half price, £19.