Jeffrey Zeldman waxes poetic over at A List Apart about the differences between Design and Art Direction. He also comments about the lack of Art Direction on the web.

I would have to agree - I have worked as an Art Director, as a designer and as a UI / IA person on the web and with software and I think the best art direction I have seen over the course of my career was in the ad agencies - where Art Direction is a practiced and learned craft. He is also correct in stating that they don't teach art direction in school. It is one of those things learned on the job - much in the same vein as apprentices used to learn from the master painters.