Richard Wallace’s Juice project (Javascript User Interface Componentised Extensions) is a “simple componentised framework constructed in Javascript to enable the sharing of Ajax Stye extensions to a web interface.”
WordPress or Scriblio users might do well to think about it as a way to put widgets on systems that don’t support widgets, though as Richard points out, “the framework is applicable to any environment which, via identifiers contained within a html page, needs to link to or embed external resources.”