CSS Sprite Generator : This tool allows you to automate the process of generating CSS sprites. Simply give it a ZIP file containing 2 or more images (GIF, PNG or JPG) and it...
Autoprefixer : PostCSS plugin to parse CSS and add vendor prefixes to CSS rules using values from Can I Use.
UnCSS : UnCSS is a tool that removes unused CSS from your stylesheets. It works across multiple files and supports Javascript-injected CSS.
Sizzy : A tool for developing responsive websites crazy-fast.
Open sourced : https://github.com/kitze/sizzy
YAML Builder : A tool for visual layout development of YAML based CSS layouts
Sprite Cow helps you get the background-position, width and height of sprites within a spritesheet as a nice bit of copyable css.