Sass
CSS preprocessor.
Frameworks
Bootstrap version 4, the most popular HTML, CSS, and JS framework for developing responsive, mobile first projects on the web.
Official Sass port of Bootstrap 2 and 3.
Modern CSS framework based on Flexbox.
A component and utility centric SCSS framework designed for rapid prototyping.
The most advanced responsive front-end framework in the world. Quickly create prototypes and production code for sites that work on any kind of device.
Libraries and Mixins
Simple fractional grid system for Sass and Stylus.
Responsive layout toolkit for Sass.
Breakpoint makes writing media queries in Sass super simple.
An extreamly powerful but easy to use Sass media query mixin.
Sass mixin that helps you compose media queries in an elegant way.
Open color is a color scheme for UI design. Available in CSS, SCSS, LESS, Stylus, Adobe library, Photoshop/Illustrator swatches and Sketch palette.
Advanced color manipulation and contrast calculation in vanilla Sass.
Using standard color blending functions in Sass.
Super easy to use Sass mixins to establish a typographic system with modular scale and vertical rhythm. Based on the Gridlover app.
Sass mixin to make responsive typography easy.
Animation
Miscellaneous
Sass mixin for creating angled edges on sections by dynamically encoding SVGs.
A flexible Sass mixin for creating BEM-style buttons.
CSS button library built using Sass and Compass.
Modular scale calculator built into your Sass.
Sass/Compass version of Normalize.css, a collection of HTML element and attribute rulesets to normalize styles across all browsers.
SCSS/CSS library to beautify checkbox and radio buttons.
JavaScript, SCSS, Sass, Less, and Stylus helpers for rendering high-resolution image variants.
Sass mixin that helps managing code deprecation.
Set of mixins for those who want to mess around with flexbox using the native support of current browsers.
The Sass implementation of lodash (API documentation).
Collection of Sass utilities to ease and improve the implementations of common style-code patterns.
Style Guides
Tools
Dart implementation of Sass.
C/C++ implementation of a Sass compiler.
Binding of libsass for Python.
Custom node-sass importer for selector specific imports, node importing, module importing, globbing support and importing files only once.
Node.js bindings to libsass.
Navigate through .scss and .sass files efficiently with the OctoLinker browser extension for GitHub.
Extract variables from scss files. Use scss to describe styles for use in javascript by extracting computed styles into js objects. Supports imports and advanced language features.
Sass loader for webpack.
Ruby on Rails stylesheet engine for Sass.
Configurable tool for writing clean and consistent SCSS. (deprecated)
P/Invoke .NET wrapper around libsass to convert SCSS to CSS supporting NET2.0/NET3.5/NET4.x+ and CoreCLR platform.