I've written about Sculpteo before, which lets you order custom 3D printed cases and accessories from its app. But its latest effort takes its capabilities a step further, which lets you create virtual works of art and then order real-life equivalents!
The app, Let's Create! Pottery HD ($4.99) is a partnership of Sculpteo with Infinite Dreams, letting you create artwork and generate it in 3D.
Let's Create! Pottery stands on its own as a fun, beautifully-designed app, which my kids have used for some time.