del.icio.us direc.tor: Johnvey Hwang's high performance AJAX web service broker. This script is very neat. Setup a bookmarlet. Visit del.icio.us. Click on the bookmarklet, and it instantly transforms your ugly del.icio.us web interface into a fancy AJAX-driven DHTML interface.
For more detailed write up, check this article on setting up a client-side web service broker.
Basically it allows you to do what Greasemonkey does, without Greasemonkey or even Mozilla/Firefox. We shall see more and more of this kind of web applications, the ones that re-write your web sites and make into their own.