On the Zend Developer Zone, there's a article posted from Matthew Weir O'Phinney spotlighting one of the handy features of the Zend Framework - Action Helpers.

Action Helpers in Zend Framework are often considered a fairly arcane subject, something for experts only. However, they are meant to be an easy way to extend the capabilities of Action Controllers, negating the need to create your own base controller with custom functionality. The aim of this tutorial is to show you how to quickly and easily create and use Action Helpers to your advantage.

He covers some of the basics - setting up a controller to extend Zend_Controller_Action - and assigning helpers to it. He looks hat hooking in events, registering and retrieving the helpers with a Broker and how to create your own custom helper. Their example is a form loader that lest you load the code for a form by submitting its class name.