- W3Schools - cheatsheets and tutorials with a live "Try It" feature.
- Zend Developer Zone - PHP from the source.
- The PHP 101 tutorials are where I started learning PHP back in 2001.
- Bob's Guides - lots of tutorials and a great blog.
- A List Apart - articles and tutorials for web designers and developers. The Evolution (and early Revolution) Manager main menu was originally based on one of their articles Hybrid CSS Dropdowns.