SimpLESS »

“Save your *.less file and, BOOOM, SimpLESS generates a 100% valid standard CSS document out of it. No further steps, it’s that simple.”

Prefix free »

“lets you use only unprefixed CSS properties everywhere. It works behind the scenes, adding the current browser’s prefix to any CSS code, only when it’s needed.”

Scout »

“Compass and Sass without all the hassle… a cross-platform app that delivers the power of Sass and Compass to the hands of web designers.”

LESS.app For Mac OS X »

An app that autocompiles .less files into CSS. I like this idea much more than having JS do the work on the front-end, or for that matter, having the server-side scripting language like PHP or Python compile it.

Re-tabulate »

A great breakdown on how to switch the order that the content and navigation is displayed based on the browser size, using CSS. A key component to truly responsive Web sites and apps.

Prefixr »

Paste your CSS into Prefixr and it will automatically add vendor prefixes for CSS3 properties. Even better, there’s an API available, so you can automate the change or hook into it from your favorite IDE.

Smoosh »

via @joemccann
A command line tool “for packaging your CSS & JavaScript projects. It will lint your JavaScript with JSHint, then build and minify your files (if you’d like) with UglifyJS for JavaScript, and Sqwish for CSS.”

CSS Lint »

We’ve gone too long without a good lint tool for CSS. This one provides syntax checking and applies “a set of rules to the code that look for problematic patterns or signs of inefficiency. The rules are all pluggable, so you can easily write your own or omit ones you don’t want.”