Bourbon

bourbon.io

• preprocessor

A simple and lightweight mixin library for Sass.

Compass

compass-style.org

• preprocessor

Based on the Sass stylesheet language, Compass is the greatest stylesheet authoring framework in the universe.

Harp

harpjs.com

• preprocessor

The open source, static web server with built-in preprocessing. Sass, LESS, Stylus, CoffeeScript and Markdown

Koala

koala-app.com

• preprocessor

Koala is a GUI application for Less, Sass, Compass and CoffeeScript compilation, to help web developers to use them more efficiently. Koala can run in windows, linux and mac.

Less

lesscss.org

• preprocessor

Less extends CSS with dynamic behavior such as variables, mixins, operations and functions. Less runs on both the server-side (with Node.js and Rhino) or client-side (modern browsers only).

Myth

myth.io

• preprocessor

Myth is a preprocessor that lets you write pure CSS without having to worry about slow browser support, or even slow spec approval. It's like a CSS polyfill.

PostCSS

github.com/postcss/postcss

• preprocessor

PostCSS is a tool to transform CSS with JS plugins. Like Sass, but modular and much powerful.

Sass

sass-lang.com

• preprocessor

Sass is the most mature, stable, and powerful professional grade CSS extension language in the world.

Scout

mhs.github.io/scout-app

• preprocessor

Scout is a cross-platform app that delivers the power of Sass & Compass into the hands of web designers.

Stylus

learnboost.github.io/stylus

• preprocessor

Stylus is an innovative stylesheet language that compiles down to CSS. Inspired by SASS, Stylus is built with node.js.