On the Zend Developer Zone, there's a new article that examines one of the key components to just about any framework out there - the front controller.
Like Action Helpers, which I've discussed in a previous article, Front Controller Plugins in Zend Framework are often considered an esoteric, advanced subject. They are, however, remarkably simple to implement, and provide an easy way to extend the functionality and behavior of your entire web application.
The article (from Matthew Weir O'Phinney) looks at the hooks defined in the controller, like routeStartup and preDispatch, and how to work with the controller to add in/get plugins from it. He provides a two examples too: Application Initialization Plugin and a Caching Plugin.