If we're discussing JS client MV* frameworks, take a look at the demos of the various options (including Ember.js, Backbone.js, Ext.JS, AngularJS) on:

http://addyosmani.github.com/todomvc/

I've been getting into AngularJS myself, which is positioned as an alternative to Backbone, KnockoutJS, etc.:

http://stackoverflow.com/questions/9588921/ember-js-vs-angul... http://zdam.posterous.com/angularjs-vs-knockoutjs-knockout-g...

(AngularJS is undergoing a flurry of development so don't use the v0.9.19 branch on the site - instead, wait for v1.0 to be released, since v1.0.0rc2 is already out. http://angularjs.org/#/ )