WordPress Plugin Development

http://codex.wordpress.org/Writing_a_Plugin
http://codex.wordpress.org/Plugins
http://codex.wordpress.org/Plugin_Resources
https://www.packtpub.com/books/content/anatomy-wordpress-plugin
http://chrislema.com/create-a-wordpress-plugin/
https://www.udemy.com/blog/how-to-make-a-plugin/
http://www.elegantthemes.com/blog/tips-tricks/how-to-create-a-wordpress-plugin
http://www.hongkiat.com/blog/beginners-guide-to-wordpress-plugin-development/
http://www.smashingmagazine.com/2011/09/30/how-to-create-a-wordpress-plugin/
http://www.itworld.com/open-source/365582/how-build-wordpress-plugin-beginners