knockout.js

official website 

http://knockoutjs.com/

Cascading drop down with knockoutjs and ASP.NET MVC

http://www.dotnetexpertguide.com/2012/06/cascading-dropdown-knockoutjs-aspnet.html 
http://www.cnblogs.com/rubylouvre/archive/2012/06/17/2551907.html 

http://www.cnblogs.com/n-pei/archive/2011/12/23/2299217.html