Additional points of reference:
Thickbook.com - Accompanies books by Juli Meloni. It has loads of really simple code snippets, tutorials, etc. Note that this is really simple stuff, but it'll keep you going for a good while.
PHP Resource Index - By Matt Wright (who also runs CGI Resource Index. Packed full of examples, tutorials and pre-written scripts.
Devshed - Excellent for all web-related programming languages.
PHP.net - The official PHP site. In partcularly, look at the Quick Reference area, which lists all of the in-built functions.
From Php.net, get yourself signed up on the newsgroups (through Outlook Express).
PHPBuilder.com
PHPMyAdmin - manage your MySQL database using this free tool (yes, you get a database with f2s.com too).
I think that covers it. If anyone else uses any resources I've not listed, I'm all ears.