Jakub Steiner is an artist that works on Linux icons and interfaces at Novell. He is responsible for much of the look and feel of the Gnome icon set.
This week, he posted a fascinating movie of his illustration process. He was drawing a small dog/puppy icon for a notification panel applet and recorded the entire illustration process.
As he suggests, you should watch the video at a high speed, since it would be a bit long to watch the whole thing in real-time (about 10 minutes). I’ve re-encoded his video at a faster speed: download the high-speed version of Jakub’s video.