Jack Slocum mashedup WordPress’s comment system with Yahoo!’s UI.  Very neat project as Jack describes,

I think it turned out to be a perfect example of what can be done in a very small amount of time with Yahoo UI and YAHOO.ext. In a day’s worth of work, I have completely transformed the comments system on this site. Around half of that time was spent on the user interface, and the other half modifying WordPress to do the things it needed to do on the backend.

The system looks nice and it speeds up page loads as the comments are posted via Ajax.  NICE!