WordPress Tutorials for Developers & Designers
Even though I've been developing WordPress Web sites for lots of clients over the passed few years, I still found Lynda.com's WordPress Tutorials very useful.
They offer a few quite updated WordPress Tutorials
- Creating and Editing Custom Themes
- WordPress:Creating Custom Widgets and Plugins with PHP
Their price is so reasonable that you may be surprised to find their video tutorials are of very high quality too. The instructors are all experienced WordPress old-timer and developers. You may give it a try for free for 7 days!
Promote a 7-day free trial to lynda.com.
Once you create an account, just search for "WordPress" and you can start learning right away. After you finish the courses, you can get an online certificate like this one: