What the heck is a JavaScript Task Runner?
Grunt is a command line tool that runs on Node.js and automates your JavaScript build process.
Grunt is an “easy” way compile coffeescript, sass, compass. It can minify, concatenate, and a whole lot more. Everything is simple… as long as you know what you’re doing.
I put the install process for both Node.js and Grunt in the post on Trimming CSS Fat.