I've reviewed Diptic in the past. It's a great iPhone app for creating photo collages on the fly. Now, Diptic PDQ (US$0.99, universal) gives you many of the same features with a new look and a quicker workflow.
The developers call it a "stripped down" version of Diptic, but don't let that fool you. Diptic PDQ has the same wide feature set, but far fewer design templates. While Diptic has 200, Diptic PDQ offers just 35 templates.
It's easy to manipulate your image within the frames for the best composition, and you can adjust the size of each frame. Images can be zoomed and rotated, and reversed for a mirror image. Borders can be customized by color and size. There are 14 filters you can apply to your images.