This is a no brainer plugin and gets installed on every wordpress site right out of the gate. It allows you to easily add scripts and code to your headers and footers. The most common application is google analytics tracking code or other verification codes.
Insert Headers and Footers is a simple plugin that lets you add scripts like Google Analytics to your WordPress site without having to get your hands dirty in code. Moreover, the simple interface gives you one place where you can add all of you scripts rather than dealing with dozens of plugins.
Posted by Daniel