I happened on the Introduction announcement for Ubiquity this morning and found it to be an awesome idea. There is a video with usage examples on the announcement page that will give you the whole scoop.

Basically it brings the power of tools like Launchy and QuickSilver) to the browser (Firefox in this case). You can create your own mashups and get things done on the browser and internet-in-general with greater ease. I am going to install it and give it a try… I will be keeping an eye on this project.

Update: I have created a command for Ubiquity and a page for future commands.