If you're the type of person who uses a lot of search engines and doesn't mind having a toolbar installed, you might want to check out Firefox Super Search. This Firefox-only add-on puts the power of 160 search engines in one toolbar, with about 70 that can be searched right from the toolbar itself.

If you're used to Firefox's built-in search box, this is a pretty big step up both from selecting one engine at a time and having to add additional engine tools from Mozilla's catalog. It's also laid out in a really straightforward manner, putting search engines with which you can search (from within the toolbar) in drop-down menus on the right side of the query box. There's also a directory of the other 90 or so engines that require a visit before beginning a new search.

Super Search is set up to let you search from nearly 70 search engines right from the blue options on the right of the search box. And the green button on the left is a directory of ones where you have to begin the search from that particular site. (Note, this screenshot has been edited to show off all of the toolbar's features at once).

My only qualm is that you cannot reorganize the order of the engines or make a shortlist of your favorites. It's also missing out on modern search box niceties like auto-complete and search-as-you-type suggestions--two things that require the search box to know which engine you're searching with first. On the plus side, though, the curation and organization of the engines is spot-on.

Note: This add-on is experimental, which means that it may not work perfectly in your browser. We used Super Search on Firefox version 3.5.1 without issues.