It's open source and available on github. This is Grunt's website.
In this blog post I want to show you how to install it and how to automate a few common tasks.
Hopefully it will convince you to drop everything you are doing and you'll find yourself adding grunt to your current project.
* Installing Grunt
* Compiling stylus files into css
* Minimize css files
* Watch for file changes and do stuff
Via Jan Hesse