Johnvey Hwang's del.icio.us director is a tour-de-force of web service and AJAX programming. The result is a cleanly designed interface for the del.icio.us power user.
However, this inudced the notion that AJAX just means Flash, except with stone age development tools, implemented slightly differently across the major browsers, and a retrograde user interface API? But look ma! No propietary plug-ins!
It's so broken it just might work.