There are a lot of webinars out there begging for developers to participate. Many contain quality content that is useful to developers; others, not so much. As a company who builds tools for developers, most assume Zend's webinars are nothing more than ads for their products; this is why we don't assume things. In reality, about 1/2 of their webcasts feature prominent members of the PHP community talking about open source tools that developers will find interesting. Here are a few of the recent ones.
Some of the topics that were presented include using PHP 5.3 namespaces, new SPL features in 5.3, unit testing in the Zend Framework and the powerful combination of the Zend Framework and Doctrine. You can find these recordings on Zend's Recorded Webinars page.