I have always been intrigued by the idea of using a client-side application to act as a service broker, integrating various services like Google Maps, Flickr, and del.icio.us. Unfortunately, after doing the research, I found that the security blocks in the browser prevent normal untrusted code to poll sites that are not from the same server, so that grand service idea couldn't be a reality. What I was able to do, though, was provide a service for a single website: del.icio.us.
Part research, part appreciation for del.icio.us, del.icio.us direc.tor is a prototype for an alternative web-based rich UI for del.icio.us. It leverages the XML and XSL services of modern browsers to deliver a responsive interface for managing user accounts with a large number of records. Try it out, and let me know what you think.