The built-in search bar in Firefox can be ciustomized to include a lot of different search engines. To add a or change the search engine used, click on the little arrow in the search bar (shown in this image).



Once you click on the arrow, you'll get an arrow that shows your existing search engine options. You can select one of these, and it will change the search engine used for searches in Firefox.

If you want to add a new search engine (and there are a *lot* that can be added), select Manage Search Engines... from the menu. This will give you a page of search engines that can be added.

Another thing to look for is when the arrow starts glowing blue (shown in this image).



When the arrow glows like this, it means that the site you are currently visiting has a search widget available for Firefox. If you click on the arrow, there will be an additional option called Add <sitename> (where <sitename> is the name of the site you are on) right above the option to manage your search engines. Selecting this option will add the search widget for the current site.