I am now using yubnub for my search engine. It's pretty neat, basically a way to add search keywords that dispatch to different kinds of searches.
For example, now instead of typing something in my search box and getting back the google results, I type 'google blah' to get back the google results. If I want to search the ubuntu package archive instead of google, I type 'upkg blah'. If I want to search launchpad for bugs related to thinkpads, I just type 'ubs thinkpad'. Very handy shortcuts!
It was always possible to define this kind of shortcuts using firefox bookmarks by setting the keyword property. The real usefulness here is the social aspect, that I can use the commands other people have created, and easily add my own. And you can do 'ls blah' to search for commands related to blah.