Back in the day, the CSS Zen Garden was a place to showcase the power of CSS. A single page was redesigned in vastly different ways with no change to the HTML. The CSS1k project (head up by Jacob Rask) is in that same vein only you are limited to only 1k of CSS. Fun, but the purpose is to get you thinking about how to be efficient and size economic with CSS.
DigitalOcean joining forces with CSS-Tricks! Special welcome offer: get $100 of free credit.