WordPress plugin development links

While developing Basic-SEO I’ve found the following sites very useful for reference purposes:

WordPress Plugin Repository – http://wp-plugins.org

You can’t beat learning by example, here you can browse the source code of all the plugins WordPress.org hosts.

WordPress PHP Documentation – http://phpdoc.wordpress.org/

All the comments from the WordPress source code extracted in HTML format and correctly linked, very useful for looking up functions.

WordPress Hooks Database – http://adambrown.info/p/wp_hooks

Database of all the action & filter hooks that have ever been available in any WordPress release and where it occurs in the source code.

WordPress Codex – http://codex.wordpress.org/

The official documentation for WordPress, has a very useful developer documentation section.