On the top right hand corner of firefox search bar, if you click down, you can add more search engines. How about creating your own search plugins!
A search plugin allows you to access a search engine right from your browser. The Mycroft project provides a collection of search plugins (over 6000) for browsers using Apple’s Sherlock standard including Mozilla Firefox and Mozilla Suite. A major difference between Mycroft search plugins and Sherlock search plugins, is that Sherlock plugins are distributed in a binary format and Mycroft plugins are not.
Learn to create your first search plugin. Advanced Mozilla-Search Plugin Documentation provides technical information on the full spectrum of the Mozilla-Search plugin capabilities. Then test your plugin against the quality guidelines. You might try the search plugin generator to help you through the process of creating a search plugin. SearchPluginHacks Firefox Extension allows easy uninstalling of search plugins – just right click on a search plugin and choose ‘Delete’. Then provide search plugins on your website.