Stylus - EXPRESSIVE, DYNAMIC, ROBUST CSS

Stylem - A user style manager for Pale Moon, Basilisk, Interlink, SeaMonkey, and other Mozilla-based software. Install styles from userstyles.org to change how web pages and the application look.

Stylecow - CSS processor to fix your css code and make it compatible with all browsers

Wikiwand - A beautiful new interface to Wikipedia

PostCSS - Increase code readability. Add vendor prefixes to CSS rules using values from Can I Use. Autoprefixer will use the data based on current browser popularity and property support to apply prefixes for you.

FreeStylerWs - Styles and skins for all popular sites in the web