Matthew Weier O'Phinney has a recent post to his blog giving a quick introduction to the Zend_Application component of the Zend Framework and how it can be used to create custom resources.
Zend_Application works in conjunction with Zend_Application_Bootstrap, which, as you might guess from its name, is what really does the bulk of the work for bootstrapping your application. It allows you to utilize plugin bootstrap resources, or define local bootstrap resources as class methods. [...] Additionally, Zend_Application_Bootstrap provides for dependency tracking (i.e., if one resource depends on another, you can ensure that that other resource will be executed first), and acts as a repository for initialized resources.
Matthew gets right into the code, looking at how to create a simple bootstrap (for the "zf" command line tool to make the project) and the contents of the application.ini file. From there he looks at creating resources - bits of code that can be executed as a part of your bootstrapping process. His example shows the implementation of "_initCurrency" and "_initRegistry" methods.