Alexander Netkachev has posted a quick tutorial today to his blog about how to use the Zend Framework (specifically the Zend_Feed component) to create an XML feed for your site.
This article explains basics of content syndications and demonstrates how to use Zend Framework Zend_Feed classes for consuming a news feed of your site.
His format of choice is Atom, slightly different from the RSS most sites use. He includes a sample document to show some of the differences (assuming you know the RSS format, of course) - both complex and simple versions. Also included is a UML layout of the Zend_Feed class, showing all of the methods and properties therein.
With the groundwork laid, he starts on the sample application - creating an Atom feed from a PHP array of data. He grabs the information from the database and pulls it into the controller where it's parsed and massaged into the array format the output needs. Then it's just a matter of passing it to the view and voila - an Atom feed worthy of consumption.