I don't know when this was released, but the search field on apple.com is slick. It seems every day some hotshot AJAX programmer (or WebObjects guru) comes up with some new magic once reserved for desktop applications, not web page frontends. In this case, Apple's search function does a real time database search and populates a dynamic popup menu with images and text, all of which updates after every keystroke.
Type in "boo" and you get this:
Add a "t" and you get this:
Quick, slick and cool.