webdev

Sauce Labs: Cloudified Browser Testing
16 Vital Checks Before Releasing a WordPress Theme | Nettuts+
Simply Testable professional automated front-end web testing
scottjehl/Respond
ie7-js – A JavaScript library to make MSIE behave like a standards-compliant browser. – Google Project Hosting
addyosmani/js-shapelib
A Better Android Emulator – Manymo
Selectivizr – CSS3 pseudo-class and attribute selectors for IE 6-8
Git on WP Engine
WebPagetest – Website Performance and Optimization Test

This is the one the WP Engine guys recommend.