Stylebot - Change the appearance of websites instantly. Preview and install styles created by other users on stylebot.me
FreeStylerWs - Styles and skins for all popular sites in the web
Dark Reader - Reduce eye strain in your browser with this extension that provides a dark theme for browsing.
Stylus - EXPRESSIVE, DYNAMIC, ROBUST CSS
xStyle - A user styles manager for the Web
Stylus - User Styles Manager - Stylus is a userstyles editor and manager based on the source code of Stylish version 1.5.2.