Normalize.css is a small CSS file that provides better cross-browser consistency in the default styling of HTML elements. It’s a modern, HTML5-ready, alternative to the traditional CSS reset.

MathJax is an open source JavaScript display engine for mathematics that works in all modern browsers.

Nice overview/reference/tutorial on using floats in CSS.

(this is obviously talking about those OTHER programmers, but...)

This looks to be a useful CSS debugging tool, especially to duffers like me...

We’ve taken a close look at some of the most interesting and useful CSS tricks, tips, ideas, methods, techniques and coding solutions and listed them below. We also included some basic techniques you can probably use in every project you are developing,