The main PHP.net website has posted a list of people participating in this year's Google Summer of Code project on various PHP projects. These include:

• PHP Optimizer by Samuel Graham Kelly IV, mentored by Derick Rethans
• gsoc:2008 - XDebug by Chung-Yang Lee, mentored by David Coallier
• PHP Bindings for Cairo by Akshat Gupta, mentored by Anant Narayanan
• Implement Unicode into PHP 6 by Henrique do Nascimento Angelo, mentored by Scott MacVicar

You can check out more information on the projects (including links to their individual pages) on this page of the Google Code website.