Rated 5 out of 5 stars
I was happily using Shadow912's version in Firefox 8, but then I upgraded to Firefox 9 and the extension broke :(
I couldn't live without it so I went ahead and fixed it :)
You can get it here: http://dl.dropbox.com/u/976471/conquery-1.7.3-mod9.xpi
I also made it possible to customize the query when right-clicking the search engine, just like when pressing Ctrl.
Keep in mind that this version will only work on Firefox 9+