Prepros - Compile Less, Sass, Scss, Stylus, Jade, Coffeescript, Haml and Markdown with live browser refresh.
LiveReload - LiveReload 2 proudly presents… The Web Developer Wonderland. (a happy land where browsers don't need a Refresh button). CSS edits and image changes apply live. CoffeeScript, SASS, LESS and others just work.
CodeKit - CodeKit allows you to optimize the performance of your website by automatically and efficiently compiling a variety of popular languages.
Browsersync - Browsersync makes your tweaking and testing faster by synchronising file changes and interactions...
Fire.app - Fire.app is a menu bar only app for dead easy HTML prototyping.
Compass CSS - Compass is an open-source CSS Authoring Framework.