PHOTOS: App Store's most-downloaded free apps by category

With more than 1.5 billion apps already downloaded from Apple's App Store, the ubiquitous iPhone continues to find ways to make itself a fixture in its users' daily lives. But 1.5 billion downloads? Of what? According to some sources, there are nearly 60,000 unique apps available, paid and free.

Click here to see the No. 1 free app in each of 20 categories offered at Apple's App Store.

Click here to go to a slideshow of the top paid apps.