I'm researching HTML5 History API, and curious what popular websites are using it. I realize only using History API isn't practical considering IE9 and older browsers don't support it, so I'm more interested in those websites that are using a History API library that provides hash-bang fallback support, such as history.js.
Facebook and Pinterest, off the top of my head. Twitter is also reportedly moving to pushState from hashbangs (finally). I'm assuming Facebook has rolled their own solution. Pinterest appears to be using Backbone.js, though I wouldn't be surprised if it isn't vanilla.