NFB StopMo Studio is a complete stop-motion utility for iPad that not only teaches you the basics of stop-motion animation, but lets you shoot your first stop-motion film as well. The application was actually born from the National Film Board of Canada's "legendary animation workshops," and concentrates "decades of expertise" to make it the App Store's very best stop-motion tool.
The app features a wide variety of capture tools including time-lapse features, access to both front-facing and rear-facing cameras, "onion skins," a grid tool, and more. Additionally, after you've shot your stop-motion film the app also provides many editing features such as the ability to add an iTunes soundtrack, add fade-in, fade-out, and sound effects, and the ability to export your film to MP4 format.
You can get NFB StopMo Studio from the App Store for $0.99. The app is only compatible with iPad.
Check out the below stop-motion video, which was made with the StopMo Studio app: