Although you can choose from more than 600 exercise activities, the coolest part about this app is that it allows you to design or pick a pre-planned interactive route for pretty much any outdoor workout using your smartphone's GPS. Get your workout stats—distance, time, pace, calories burned, etc.—and compare and share them with the greater MapMyFitness community via Facebook and Twitter (they’re said to have more than 20 million users). You can also sync the app with other fitness gadgets, like Fitbit and Nike+.
Cost: Free, $5.99 for bonus features
Available in: iTunes App Store