I shoulda mentioned that the new DC logo was designed by Josh Beatman of Brainchild Studios, and that the 70's version was the work of Milton Glaser, who's been responsible for some of the most memorable insignias in the field of graphic arts.
The earlier version went through several incarnations before it became the version I posted in the previous message, but I believe most of them were the work of Ira Schnapp, who was the in-house lettering genius at DC Comics or National Comics or whatever you want to call it. Mr. Schnapp also designed most of the famous logos, including the Superman one we all know and love.