Sblack is a little free Mac app that applies a Dark Theme to Slack for Mac to make it easier on your eyes. Just drag and drop and you're done!
Darkness is a Chrome extension that provides dark themes for popular websites
Dark Mode List is a list of apps and sites that support dark mode
Darkdocs adds a dark mode to your Google Docs writing experience.
Enjoy Instagram web in the new night blue colors and protect your eyes
Dark Mode for Safari is an extension, similar to Google Chrome extensions, that provides a better way to enjoy surfing the web by using a dark theme.
Dark Reader for Safari makes all websites dark, relaxing your eyes. Perfectly suits to macOS Mojave dark mode.
Iris is software which makes Monitors healthy for the eyes.
With Iris you can reduce the Blue Light emitted from your screen for better sleep, reduce the Brightness of your screen without PWM and avoid eye pain.
The science behind Iris:
HappyOwl is a FREE chrome extension to turn night mode on for medium.com
Berry is the iPhone and iPad browser that automagically makes all websites dark, blocks ads/trackers, increases battery life, and much more. Berry even includes a Today widget and dark keyboard that can be used in any app.