I've been playing with it for months on my iPhone, but now it's gone public – Autodesk's Sketchbook Mobile is coming to the app store. A fantastic addition to the digital designer's workflow, this is the drawing app you've been waiting for if you're a professional designer or digital artist.
Check out Carl Alviani's article about it on Core77, and I'll be putting up my impressions soon.
Inspired by Jorge Colombo's cover of the June 1, 2009 issue of The New Yorker, I did a quick sketch in my living room using the Brushes app on my iPhone. Although it's far from cover-worthy, it is fun to play with and a great tool for forcing looseness into your sketching.