WordPress Code Resources
* WordPress Codex – The official online manual for WordPress and a living repository for WordPress information and documentation.
* Daily documentation – Receive info about only one WordPress function reference by mail everyday for free.
* CodewithWP – Code With WP teaches you not only how to get things done in WordPress, but also how to get things done right in WordPress.
* QueryPosts – User friendly WordPress code reference.
* phpdoc – Official reference accessible from plugin and theme editor in the WordPress dashboard.