del.icio.us direc.tor: Delivering A High-Performance AJAX Web Service Broker: If you are a del.icio.us user, this application will make you weep. Seriously. It makes me wish I used del.icio.us more so I had more to do on my page. Insanely well-done.
A great example of a remix — these days, if you don’t like how a site works, just change it.