Lookpick is a project mainly written in JavaScript, it's free.
Firefox add-on for online search plugin management.
A Firefox add-on that replaces the search bar in the upper right. It fetches a list of search plugins that can be managed and personalized at lookpicking. Search engines can be selected by typing in the first few letters and then select one of the autocomplete choices.
It has yet to be made compatible with FF 4, which I am hereby setting out to do ;)