Google's Material Design is a great reference as well. http://www.google.com/design/spec/animation/authentic-motion.html#

This is a great post but it has been around for a while... I would find the other posts but I can't be bothered.

If your interested, you should definitely watch his talk which he links to at the bottom of this post. https://www.youtube.com/watch?v=TMe0WnkF1Lc&feature=c4-overview&list=UURx1y52pfeMwbuer9Vh2u-A