jQueryの次の世代、 新世代JavaScriptライブラリたち

5 JavaScript Libraries You'll Love

Backbone, for adding structure to large JavaScript-based web apps.
Underscore, a utility-belt library that adds functional programming features to JavaScript.
Knockout, a great way to simplify your user interfaces.
Sugar, which extends the JavaScript language with a wealth of useful methods.
CoffeeScript, a language that compiles down to JavaScript and is really nice to work with.

CoffeeScriptなんてもうJavaScriptの範疇に入らないかも。