PHPmonkeys.com

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.