http://www.php.net <- This is the main resource for PHP, and proablly one of the best. The built in function look up is one of the best features around.
http://www.phpbuilder.net <- Good for getting started, although this site is starting to show its age (less and less articles are being posted)
http://www.webmonkey.com <- Good beginner tutorials, some advanced stuff, but the beginning tutorials are very good
http://www.zend.com <- Good information and bit of code or entire scripts. The engine behind PHP, and has some software for those running big sites and looking to pay some money
http://www.firepages.com.au <- A site run by firepages, containting the phpdev bundle, an easy to use bundle for windows containing apache, php, mysql and perl