php|architect magazine (http://www.phparch.com) has just launched a new mailing list dedicated to PHP security.
The mailing list, which is moderated to ensure an optimal signal-to-noise ratio, is a good place to keep abreast of new security developments, announcements of security products and to discuss proper techniques for deploying, maintaining and developing PHP and PHP applications.
You can read all about it (and subscribe to it) at http://www.phparch.com/phpsec.