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
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.
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.