Try Graphite for free! Graphite Lite allows 2 drawings at a time and exports files with a small watermark.
Trace your photos or draw freehand! Capture form, light and shadow with Graphite's simple interface and expressive tools.
TRACE FROM CAMERA OR PHOTO LIBRARY
Import images from your photo library or camera; study the masters and learn by doing.
UNDO, REDO, and ZOOM
The most important editing features are fully supported; you can undo all the way back to the beginning of your drawing. Pinch to zoom.
PENCIL, CHARCOAL, KNEADED ERASER and HARD ERASER
Based on real physical models of pencil and paper, our expressive, natural tools adapt to your movement to create texture, shading, and highlights.
Our digital ink is fully optimized for the new iPad's Retina display; files are exported at full resolution.
Graphite makes it easy to share your work with support for Dropbox, Facebook, Twitter, AirPrint, email, and photo library.
Portrait screenshot courtesy of Da's Art: http://www.flickr.com/photos/sketchda/