Have a look: http://aghca.org/
(I may play with other effects later, so this might look different by the time you see it.)
It works fine in Safari, Chrome and Firefox on a Mac. If you see problems with other browsers or platforms, please let me know here.
I should add that I'm using Wordpress 3.0 and Atahualpa 3.5.3 on this site. It's wonderful to have the fading effect built-in as an option, no fancy JS coding required by the user.