The ‘Ultimate’ Flexbox Cheatsheet:
http://www.sketchingwithcss.com/samplechapter/cheatsheet.html
http://www.smashingmagazine.com/2013/05/centering-elements-with-flexbox/
MDN Tutorial:
https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Flexible_Box_Layout/Using_CSS_flexible_boxes
-prefix-free: a JS plugin that lets you write prefix-free CSS: http://leaverou.github.io/prefixfree/
Web Developer: http://chrispederick.com/work/web-developer/