I browsed through The Zen of CSS Design, by Dave Shea and Molly E. Holzschlag. It's a beautiful book that describes a number of the designs at http://www.csszengarden.com/. I learned a few things about CSS along the way, but I mostly learned to be glad that I'm not responsible for creating nice designs for multiple browsers using only CSS on semi-structured content. Even if I were a capable designer, it does not look like a fun task. I'm glad that there are people out there that can do it, though; the Web would be an uglier place without them.