Andi Gutmans has posted an update on the status of the Zend_Amf component of the Zend Framework to his blog today, including links to some examples and updates from other developers.
At ZendCon this year we announced a partnership between Zend and Adobe. The goal of the partnership is to help make it easier for PHP developers to use Flex. Since then there has been a flurry of activity including blog posts and the introduction of Zend_Amf into the main trunk of Zend Framework.
Some of the resources he links to include several examples written up by Kevin Hoyt showing how to get started with the component, the webinar from Matthew Weier o'Phinney and Lee Brimlow as well as a manual page for it over on RIAFox.com.