Welcome to the module developer's guide for Drupal 8!
This section includes tutorials and other information that you need to create custom modules for Drupal 8.x version.
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 (September 29, 2014)
There are updated slides available here from the MidWest PHP conference. (March 14th, 2015)
And there will be a new video of the updated presentation available after DrupalCon LA, 2015 (May 11th, 2015)
There is also a Sitepoint series on developing Drupal 8 modules that you can check out.
Note that core Drupal has moved on since this tutorial was 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.