Website Grader - Grade your website's strengths and weaknesses in seconds.
Prepros - Compile Less, Sass, Scss, Stylus, Jade, Coffeescript, Haml and Markdown with live browser refresh.
PageSpeed Ninja - One-click page speed boost for WordPress
Semantic Pen - Create Publish-Ready-Content in Minutes!
WebSite Auditor - The techie's SEO spider: find site issues other tools miss
Scout-App - Process Sass files into CSS without any knowledge of the command line.