Welcome to the module developer's guide for Drupal 8!
This section includes tutorials and other information that you need to create modules for Drupal version 8.x.
An excellent overview: Understanding Drupal 8
Other general resources
Several introductory screencasts walking you through setting up a basic D8 module have been published:
- Maarten De Block - Building a Drupal 8 module (DrupalCamp Leuven 15/9/2013)
- Lullabot - Creating your first Drupal 8 module (July 2013 / DEV version)
An excellent presentation on working with the Drupal 8 API Amsterdam 2014: Drupal 8: The Crash Course
Alex Bronstein wrote an introductory article titled "Drupal 8: Hello OOP, Hello world!"
There is also a Sitepoint series on developing Drupal 8 modules that you can check out.
Note that core Drupal has moved on since both these tutorials were written, and the code no longer works without error. You can find some explanation of the changes needed, as well as links to the updated code here.