The number of calories burned depends on how fast you go. An average 150-pound person can burn anywhere from 570 calories if she jogs at 5 miles/hour, or 900 if she keeps an 8 mile/hour pace. At a pace of 6 miles/hour, a runner burns about 680 calories in 60 minutes.

Yoga can be a tough cardio routine or a relaxing, meditative experience. Vinyasa yoga, which keeps you moving and flowing from pose to pose, burns around 600 calories an hour. For comparison, a hatha or relaxing class uses around 175 calories in 60 minutes. (Be sure to calculate your calories based on active yoga time, not meditation, chanting or savasana.)

A session of table tennis burns about 270 calories an hour (and that's about four or five regular games). 

Pushing a lawn mower around for an hour is great strength training for your shoulders and arms, and it provides a solid cardio workout. It burns about 300 calories in an hour. (Bonus: If you use an old-fashioned reel mower, you'll get a beautiful lawn sans carbon emissions and noise pollution!) 

You can walk almost anywhere, so if you can't fit in a workout, just hoof it. If you keep a fairly brisk pace, you'll burn 350 calories an hour. 

If you ride for an hour and are trotting most of the time, you will burn 440 calories. (Think of how many the horse must be using!) If you are walking, you'll only burn 170, so on your next trail ride, get your heart rate up and your thighs working with a faster pace. 

A smooch session will burn through about 50 calories in half an hour, and sex itself will burn 140 calories in half an hour, so if you want to skip the gym, go slow when it comes to intimate time with your partner, and blast 190 calories the fun way.  

An hour of Pilates burns 240 calories, though if you do it regularly, it tightens and tones muscles more than some activities that burn more calories. 

Washing a car is a great workout; between hauling your hose around, sudsing the exterior, rinsing and waxing and then vacuuming the interior, it takes time and energy (about 300 calories per hour ). So save some cash by skipping the drive-through and burn some calories instead. 

Weightlifting only burns about 220 calories an hour, but there's new evidence that you burn more calories after your exercise session if that exercise is weightlifting. So, you might only burn 220 calories while you're lifting, but you will continue to burn calories in the next 24 hours; with cardio, you might burn 350 calories during your exercise session but you will not continue to burn many more calories post-exercise.

Yes, if you're pushing as hard as your teacher's encouragement will make you go, you can burn up to 850 calories in an hour of spinning. But even tough spin classes are usually only 45 minutes long (and there's a 5-minute cooldown and warm-up), so keep that in mind. 

Snowshoeing burns about 500 calories an hour and downhill skiing burns about 350. If you're doing either of those activities all day in the cold, you'll need some serious (but healthy) food to keep you going.