While browsing around on the internet, I stumbled upon a forum posing the question "Can you actually lose weight through sex?" The answer was, unsurprisingly, yes! Sex IS a form of movement, movement is exercise. (And for some of us, it's really vigorous movement.)
This article from Woman's Day magazine breaks down calories burned through sexual activity, including undressing. (A whooping 8 to 10 calories) A man can burn up to 80 calories just trying to remove a bra - with his mouth.
A woman squatting, bouncing on top can burn up to 207 calories in a half an hour while toning your calves and thighs. Regular cowgirl position is known to burn over 144 calories per half an hour.
Oral sex can burn 100 calories. Adding push ups puts it up to 171, while adding yoga can put it to 135 calories.
This article from the Daily Muscle adds masturbation into calorie burning. An average masturbation session can burn 100 to 150 calories, while doing a 5 minute vigorous masturbation session can burn almost 300 calories.