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.
Website Image Speed Test - Beautiful & easy free analysis of the images on your page
Browsersync - Browsersync makes your tweaking and testing faster by synchronising file changes and interactions...
Checkbot - Checkbot will boost the SEO, speed and security of your site by checking you're following 50+ web best practices. Browser extension with free and paid plans.
CodeKit - CodeKit allows you to optimize the performance of your website by automatically and efficiently compiling a variety of popular languages.
Smaller - Make your websites load faster