PHPmonkeys.com

www.docblox-project.org - A PHP 5.3 compatible API Documentation generator aimed at projects of all sizes and Continuous Integration

openshift.redhat.com - A cloud-based application platform for PHP, Java, Perl, Python, and Ruby applications

www.addedbytes.com - Handy reference listing date format arguments, regular expression syntax and other common functions.

ocw.mit.edu - Free electrical engineering and computer science courses from MIT.

www.slideshare.net - Helpful tips for using vim with PHP, or any other language for that matter.

http://ostatus.org/ - OStatus is an open standard for distributed status updates

framework.zend.com - Extending the art & spirit of PHP, Zend Framework is based on simplicity, object-oriented best practices, corporate friendly licensing, and a rigorously tested agile codebase.

http://elgg.org/index.php - A powerful open source social networking platform written in PHP