CSS

CSS Framework

• jgthms/bulma - Modern CSS framework based on Flexbox

Design

• froala/design-blocks - A set of 170+ Bootstrap based design blocks ready to be used to create clean modern websites.

Design System

• pinterest/gestalt - A set of React UI components that supports Pinterest’s design language
• concrete-utopia/utopia - Design ❤️ Code
• Shopify/polaris - Shopify’s design system to help us work together to build a great experience for all of our merchants.
• tachyons-css/tachyons - Functional css for humans

headlessui

• tailwindlabs/headlessui - Completely unstyled, fully accessible UI components, designed to integrate beautifully with Tailwind CSS.

Animation

• h5bp/Effeckt.css

CSS-in-JS

• ben-rogerson/twin.macro - 🦹‍♂️ Twin blends the magic of Tailwind with the flexibility of css-in-js (emotion, styled-components, stitches and goober) at build time.