With over a million apps in the iTunes store for your smartphone, it's easy to be overwhelmed with the choices. One free app we like at Do Just One Thing is called the Energy Cost Calculator, which helps you figure out exactly how much energy your electronics, appliances and other major energy hogs in your home actually use. Just type in your estimated usage of an item, what your actual cost per kilowatt of energy is (it's on your electric bill) and voila! It tells you what you're actually paying per item. It's an easy way to help you prioritize to save energy and money at home.