http://caloriecount.about.com/calories-burned-sexual-activity-active-a368

Activity Expenditure Details
Activities > Sexual Activity
Calories burned with Sexual Activity, Active

Vigorous Effort

102 calories per hour

Assuming a body weight of: 150 lbs
This is equivalent to eating any of the lines of the following table.
Quantity     Description     Cals
0.4     Grande Starbucks Caffe Latte - Made with whole milk     272
0.1     McDonald's Big Mac - With cheese     704
1.3     Glasses of wine (3.5 fl oz)     79
0.4     Snickers Bar     273
0.5     Cans of Coca-Cola     207
3.4     Carrots     30