wp_links

http://premium.wpmudev.org/

http://www.wpgreece.gr/

http://wprocks.com/

wp-themes

http://www.freewebtemplates.com

http://andreasviklund.com/

http://www.freewordpressthemes4u.com/

http://www.siteground.com/

http://wordpress.org/extend/themes/

http://www.justskins.com/themes/wordpress-themes

http://www.wpzoom.com/

http://wpthemes.info/

http://wprocks.com/free-themes/

http://digitalnature.ro/projects/fusion/

wp-plugins

http://lesterchan.net/wordpress/category/plugins/

WordPress Plugins Used On The Michel Fortin Blog
http://www.michelfortin.com/wordpress-plugins-michel-fortin-blog/

wp-functions , classes

http://codex.wordpress.org/Function_Reference

https://developer.wordpress.org/reference/

http://phpcrossref.com/xref/wordpress/