Scout-App - Process Sass files into CSS without any knowledge of the command line.
Sass - Syntatically Awesome Style Sheets
Prepros - Compile Less, Sass, Scss, Stylus, Jade, Coffeescript, Haml and Markdown with live browser refresh.
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.
LESS Compiler - LESS Compiler makes formatted CSS styles from less source.
Stylus - EXPRESSIVE, DYNAMIC, ROBUST CSS