AngularJS (Google-produced JS Framework)
angularjs.org
angularjs.org
Also, both Knockout and Angular require that you add non-standard attributes to your markup. Whatever happened to separation of concerns? Having used both Knockout and Backbone, I find Backbone's separation of JS and HTML to be a major benefit. Not to mention two way binding is a neat trick, but often what I'm really after is a decent structure to hang my custom script on so I can keep it maintainable. A lot of the code I wrote using Knockout is almost impossible to follow a few weeks later.