Sass - Syntatically Awesome Style Sheets
Materialize CSS - A modern responsive front-end framework based on Material Design
Material UI - A CSS Framework and a Set of React Components that Implement Google's Material Design
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.
Semantic UI - A UI Component library implemented using a set of specifications designed around natural language
Topcoat - TopCoat, TopWeb, Rheologic, Software for coating, drying, converting, web handling, industries.