Ubiquity for Firefox from Aza Raskin on Vimeo.
Mozilla Labs » Blog Archive » Introducing Ubiquity

The overall goals of Ubiquity are to explore how best to:
* Empower users to control the web browser with language-based instructions. (With search, users type what they want to find. With Ubiquity, they type what they want to do.)
* Enable on-demand, user-generated mashups with existing open Web APIs. (In other words, allowing everyone–not just Web developers–to remix the Web so it fits their needs, no matter what page they are on, or what they are doing.)
* Use Trust networks and social constructs to balance security with ease of extensibility.
* Extend the browser functionality easily.

I think Microsoft is going to copy the hell out of this and release a "Microsoft Live OpenWeb Command Window Beta" before mid-September.