CodeKit!

Koala is a gui for Less, Sass, Compass and CoffeeScript. Koala can run in windows, mac, and linux.

Compile Less, Sass, Scss, Stylus, Jade, Coffeescript, Haml and Markdown with live browser refresh.Prepros is a web design & development tool that does all the heavy lifting needed to preprocess, optimize and test your sites and keeps your workflow supercharged.

Compass is a stylesheet authoring framework that makes your stylesheets and markup easier to build and maintain. With compass, you write your stylesheets in Sass instead of plain CSS.

Fire.app is a menu bar only app for dead easy HTML prototyping. It supports Sass/Compass, Haml, ERB, Markdown, CoffeeScript, and more.

Scout-App is a cross-platform desktop app that delivers the power of Sass to the hands of web designers.

A web developer tool that applies JavaScript and CSS changes without having to reload the page.

Write your LESS markup. Crunch it into a CSS file. Link the crunched CSS file in your HTML. CRUNCH allows you to organize your LESS/CSS styles into some well-organized libraries, and then just serve a single file to the browser. It also renders your page without relying on JavaScript or command-line geekery.

The life-saver app for web developers !Easily check syntax, minify or process all your web assets (stylesheets, scripts and templates) as you edit them with your favorite text editor!

Smaller is a powerful HTML, PHP, CSS and JavaScript compressor on Mac OS X, definitely a must have for every Mac based web developers.

Minimus is a GUI frontend for Yahoo’s YUI Compressor. Instead of using inconvenient and slow websites to compress your JavaScript and CSS, you can do it right on your Mac.

LivePage is a developer tool which reloads website resources (such as CSS, HTML and JavaScript) as they update on the server, so you are always looking at the most up-to-date version of a web page. It can make developing websites a lot faster, by helping productivity.