Experience a comprehensive Drupal 8 tutorial that'll help you get started.
We put together a Drupal 8 tutorial with Larry Garfield, giving a crash course on how to quickly get started with all the new stuff. In this Drupal 8 tutorial, our speaker will walk you through Drupal's key systems and APIs that are intended to give developers a taste of what building with Drupal 8 will be like. Check out this session for a comprehensive Drupal 8 tutorial which will help you get started with D8 right away.
Almost a complete rewrite under the hood, Drupal 8 is a modern, PHP 5.5-boasting, REST-capable, object-oriented powerhouse. Now leveraging third-party components from no less than nine different projects, Drupal 8 aims to be the premier Content Management Platform for PHP. But how do you use all this new-fangled stuff?
Basic patterns of developing modules for Drupal 8
How typical Drupal 7 tasks map onto Drupal 8 concepts
Leveraging existing knowledge of modern PHP and Symfony in particular, when building Drupal 8 modules.
You could also have a look at a couple of resources suggested by Larry: