I want to compile a list of the most common tools, frameworks & libs web developers are using today. Things seem to change daily with new, cool, and helpful projects announced all the time. It'd be great to nail some of these down as a reference.

Examples:

jQuery
Backbone
Underscore
Grunt
Mocha
RequireJS
HTML5 Boilerplate
Modernizr
SASS
Compass

Rebecca Murphey <a href="http://rmurphey.com/blog/2012/04/12/a-baseline-for-front-end-developers/">took a stab at this</a> a couple of months ago.

So, what are you using that makes your front-end dev insanely easier?