DropCollage

Just long-click on any image in the horizontal gallery at the top of the screen, and drag it into any field on the layout below.

Choose from seven different layouts, including a freestyle layout where you can drag, pinch, and zoom the image in any design you want. Then add text, stickers, or draw on top of your collage. You can even layer a new image on top of the whole thing, and erase it using your finger to show parts of the collage underneath. Then share your creations to Twitter, Facebook, or Instagram directly from the app.

Everything is controlled from a dropdown menu in the action bar. No other collage app lets you do so much while keeping it so simple.