Ubiquity adds intelligence to your browser… It is a Firefox plugin that interprets natural language, maps your commands to a webservice, serves your arguments to that webservice and inserts the results for you in your editing interface.
It runs a kind of macros, user-contributed snippets of javascript. It makes me think of the CoScripter project at IBM - see writeup by Jon Udell.
Ubiquity for Firefox from Aza Raskin on Vimeo.
