chrome-extension-simple-site-blocker

Shows white screen with 'blocked' message on sites you don't want to waste time on

This extension requires no special permissions and won't spy on you (check all seven lines of script if you don't believe that).

You will though have to:

• edit the site list in manifest.json to suit your own favourite procrastination sites
• install this plugin manually yourself.
  • go to chrome://extensions/, click on the Load unpacked button and select this folder