Directly related to Drupal

• Video: daily dose of drupal, first video: https://www.youtube.com/watch?v=1OLsNA8ef_E
• https://wunderkraut.se/blogg/taming-beast-learn-views-wunderkraut: learn to work with views
• https://simplytest.me/: to check the functionality of a certain module
• www.drupalfacile.org: 79 episodes with YouTube movies demonstrating Drupal modules (in French, literally: Drupal easy)
• http://drupalcursus.be: site related to the evening course I'm following (in Dutch)
• http://drupal.be/documentatie/modules-kiezen: literally: choose modules (in Dutch)
• http://www.drupalzelfstudie.be

Indirectly related to Drupal

• http://www.colorzilla.com/gradient-editor/: to generate gradient css
• http://www.webpagetest.org: test a website's performance
• http://www.responsinator.com: comparable to the "Resize Window" Chrome plugin
• https://regex101.com: site to test regular expressions
• www.mxtoolbox.com: tool to resolve general internet problems