Diptic PDQ (iPhone, iPad and iPod touch)
The free, basic version of Diptic is available for Android in addition to iOS, but the newest iteration, Diptic PDQ (Pretty Dang Quick) is only on the App Store. Both apps let you take a number of images and combine them into collages with various border styles and other effects. Diptic PDQ has an improved interface and gives you new control over the creation process, though, with additional functions to quickly swap out or switch image positions, among other things. Diptic PDQ is a must-have app all for all photo aficionados.