Ubiquity: Mozilla's Take on a Web Command Line
There's a lot of buzz right now about Ubiquity: Mozilla's attempt to explore command-based interaction within Firefox. Users of other command-oriented interfaces like QuickSilver or Enso, will feel right at home with Ubiquity: you activate it within your browser with a simple key combination, and then start typing. Depending on what you type, stuff happens.
What sort of stuff? That depends on the Ubiquity commands (think browser extensions, but with a new target) you have loaded. By default, the things it can do include plotting things on Google Maps, looking them up on Wikipedia, sending email via GMail, talking to Twitter, editing pages directly in your browser, and plenty more. But there's a documented interface for adding more commands, and Mozilla's hope is that this becomes the de facto way to enable mashups for end users (and, not incidentally, gives people yet another good reason to switch to Firefox).
I installed Ubiquity and gave it a spin, and for a 0.1 version, it works quite well. Of course, there aren't a lot of commands for it to discover yet, but given the heavy pickup in the blogosphere, that will probably change. New users should beware that this is experimental: in particular, the user interface is certain to change before the product actually releases.
A web command line isn't an especially new idea: it's been done before by folks like PodiPodi, and there's also Goosh, the Google shell. But having Mozilla's weight behind it makes it near-certain that Ubiquity will become the default software in this niche. The software is licensed under Mozilla's usual GPL/MPL/LGPL 3-way license, and you can get the source code via Mercurial - or at least, you should be able to when their source code server isn't overloaded to the point of collapse.