20 Tutorials to Develop Plugin WordPress, I collect from pelfusion.com, you can visit pelfusion.com or see below
1. WP Tutorial: Your First WP Plugin
2. Writing a Plugin
3. How to Write a WordPress Plugin – Introduction
4. Create a Custom WordPress Plugin From Scratch
5. Anatomy of a WordPress Plugin
6. A Crash-Course in WordPress Plugin Development
7. WordPress Plugin Development Short Tutorial
8. WordPress Plugin Tutorial – Hello World
9. The Ultimate Guide to Building a WordPress Plugin
11. WorPress Plugin Development with PHP
12. Tips to Speed Up WordPress Plugin Development
13. Seven Reasons to Write a WordPress Plugin
14. WordPress Plugin Actions
15. WordPress Plugin Filters
16. Constructing a WordPress Plugin Admin Panel
17. Constructing a WordPress Plugin User’s Panel
18. Using JavaScript and CSS with your WordPress Plugin
19. Using AJAX with your WordPress Plugin
20. Releasing and Promoting Your WordPress Plugin
source: pelfusion.com
20 Tutorials to Develop WordPress Plugin From pelfusion.com,