I have always been a follower of Envato’s Tuts+ sites and Wptuts+ is the newest one to join.
Wptuts+ is a site dedicated to teaching people how to use WordPress, develop widgets, plugins and themes, successfully scale sites, find interesting WordPress resources, and build a freelance business around the platform. Over 25 million people have chosen WordPress to power the place on the web they call “home”, and it’s by far and away the most successful blogging platform online.
It’s all about developing for WordPress, creating fantastic themes, and building a business around the platform. Whether you’re completely new to WordPress or you’re a seasoned pro, this is the site for you!
Visit the site at: http://wp.tutsplus.com/
Envato is a startup based out of Australia with people around the world and sites serving pages every second.