.. Not a lot, by the looks of things. Here's one example of what can be done though; it involves manually adding a class to all disabled form elements...
if nothing else, it allows the styling of the background colour and changing the font-size, weight etc... Anyway, here's the code:
For a far more detailed discussion on the subject, you can also look at these sites:
http://www.456bereastreet.com/lab/styling-form-controls-revisited/disabled/#ie6-xp
http://www.askthecssguy.com/2007/05/shawn_asks_the_css_guy_about_s_1.html
