Firefox 3 isn’t quite out yet, but already there are some exciting plans for CSS implementation in future versions.

FF3.1 should see all the selectors (test them here), @media queries, text-shadow, font-stretch, and downloadable web fonts with @font-face; FF4 should add calc() and attr() values, along with the Animation and Transitions modules proposed by the Webkit team.

You can see a list of other planned implementations on the Mozilla Wiki.