Top Related
Drupal 8 Theming Done Right (European Drupal Days 2015)
Theming drupal 7
Drupal Theming An Introduction
Forensic Theming - Drupal Theming Design, UX and Theming Emma Jane Hogbin @emmajanedotnet
Drupal 8 introduction to theming
Drupal - theming (tips)
Theming Drupal 6.x Forms
Drupal Theming Hans Rossel