I was looking for a addon much like the older FFXI Helper when I found a new extension/addon called Add-to-search-bar.
With this addon you can make the default search box in the corner of Firefox use any website's search box as a search engine from FF.
Pretty easy as I made one for ZAM, YellowGremlin, FFXIVPro, FFXIV Wiki (gamerscape), and Lodestone.
Very helpful addon. Instructions on how to use it are on the main page and the addon bar.