An exercise that's as fun as it is effective? Get jumping.

Regularly bouncing on a mini trampoline is a great way to get fit without experiencing the kind of boredom you get from lifting weights. Big trampolines work, too, if you -- or, more appropriately, your kids -- have one in the backyard. Half an hour of jumping on the trampoline burns at least 100 calories, and that time probably passes more quickly than it would if you were on the treadmill.

But you don't need a soft surface to enjoy hopping around. Jumping rope is a great way to burn a ton of calories. Jumping jacks work, too. Give either a try -- you'll be sweating up a storm in no time.