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.

A microwave oven is an energy-efficient way to quickly heat and cook foods at home. But did you know that, on average, a microwave is used only about 70 hours a year? That's about 1 percent of the year, with the other 99 percent of the time spent doing nothing. But when the microwave is not being used to heat food, it's still sucking power from the grid using "vampire power" to illuminate the display and keep it ready to go at the touch of button. It's like having a lamp on 24 hours a day, seven days a week. When you're not using the microwave, simply unplug it. You'll recoup savings and help extend the life of the appliance.

Doing some painting around the house? It's easier than ever to find eco-friendly latex paint at the store, so look for zero-VOC (volatile organic compounds) brands for your project. Measure the room and use an online paint calculator to know exactly how much paint you need, and don't overbuy. When stocking up on supplies, look for plastic roller trays, cups and paint brushes that use 100 percent post-consumer recycled plastic, which is made from items like soda bottles and milk cartons. Finally, if you want to save leftover paint, try this trick: Cover the can opening with plastic wrap, and tap the lid securely back on top. Store the can upside down (you can place it in a tray if you're worried about leakage). It will be ready to go for next time.