WordPress Codex - http://codex.wordpress.org/%D0%97%D0%B0%D0%B3%D0%BB%D0%B0%D0%B2%D0%BD%D0%B0%D1%8F%20%D1%81%D1%82%D1%80%D0%B0%D0%BD%D0%B8%D1%86%D0%B0

Функции WordPress - http://wp-docs.ru/

Русскоязычная документация - http://wp-kama.ru/

Notepad++ - http://notepad-plus-plus.org/download/v6.5.4.html

Sublime Text - http://www.sublimetext.com/3

Wordpress 3.8.1 - http://ru.wordpress.org/releases/