You know who's a big app developer? Yep, the federal government. Its agencies offer a variety of free mobile apps you might find of use. Here are three of them.
The apps range from the educational and obscure (Guide to National Statuary Hall Collection of State Statues) to the entertaining (NORAD Tracks Santa).
FoodKeeper (Android and iOS) is one of the newest ones (and the one that prompted my look at Uncle Sam's apps). Created by the USDA, FoodKeeper tells you how to store different foods and how long they last, and you can add your food products to get notified when they're about to expire.
Breath2Relax (Android and iOS) bills itself as a "portable stress management tool" and offers breathing exercises to help you de-stress. Interestingly enough, it comes from the US Department of Defense
You'll find the whole list at USA.gov. There's something for everyone in that long list, including cool ones from NASA and the Smithsonian Institute.