Step-by-step: Converting modules from Drupal 7 to Drupal 8
As Gábor pointed out, now's the time to help make Drupal 8 more unified and user/developer friendly. A great way to do that is try porting your modules, now, while there's still time to fix the APIs before code freeze.
Here's the video and slides from my Upgrading your modules to Drupal 8 talk at DrupalCon Sydney 2013, featuring the Pants module.
Slides: PDF | PPT | KEY (the canonical version)
But wait, there's more! ;)
