Firefox: If you want to compact your user interface in Firefox and turn your address box into a destination for not just URLs but searches too, Foobar combines the address box and search box into one.
If you often find yourself typing in a search command into the address box when you actually meant to use the little search box off to the side, Foobar is a handy addition to your Firefox arsenal. Install the extension and your address bar becomes a little more Spartan, the address box and search box are now one.
URLs typed into the box take you to the site, but anything outside a recognised address like HTTP, FTP or ABOUT: becomes a search in the selected search engine. In the above screenshot my entry of site:lifehacker.com.au Firefox will pull up the Google search results for Firefox on Lifehacker.com.au.
Have a handy Firefox extension — interface-altering or otherwise — to share? Let's hear about it in the comments.