pencils polymer & pixels

I haven’t had a chance to play around with this sketching tool yet but it looks interesting.  You can see a demo at atebits.com

Incredibly easy-to-use drawing tool

Advanced stroke rendering make sketches look natural

Intuitive 3D layer interface

Save to most popular graphics formats

Drawing tablet supported (but not required)

1-click sharing

Freely publish to the Scribbles Gallery

“Infinite canvas” groundbreaking core technology that allows the artist to break free of the restrictions of typical drawing apps. You never have to pre-define the size of your canvas. You can zoom into your drawings with unparalleled precision and Scribbles will magically re-render your art so you never encounter a jaggy edge or blocky pixel.

High-resolution output

Free to download and try for as long as you want

An excellent example of how prototyping works from idea to production.  Observation > Sketching > Modeling > Testing > Revising > Specification > Production.  One of the interesting things to watch for here is the level of fidelity in the methods.  Sketches, models and prototypes all advance the concept and feed back into its refinement.

Strida