Nunjucks
A jinja2-inspired templating system for javascript
Terrificjs
Terrific JavaScript Framework
T.js
A tiny javascript templating framework in ~400 bytes gzipped
Stampit
Create objects from reusable, composable behaviors.
Handlebars Helpers
A small collection of useful helpers for Handlebars.js
Backbone Nested
A plugin to make Backbone.js keep track of nested attributes.
Buster
A powerful suite of automated test tools for JavaScript.
Keymaster
A simple micro-library for defining and dispatching keyboard shortcuts. It has no dependencies.
Backbone Associations
Create object hierarchies with Backbone models; Respond to hierarchy changes using regular Backbone events.
Hasher
Browser history manager for rich media websites
Crossroads.js
JavaScript Routes
Queue
Yet another asynchronous helper library for JavaScript. 387 bytes minified and gzipped!
Swig
Take a swig of the best template engine for JavaScript.
Aload
Loads images, scripts, styles, iframes, videos and audio asynchronously.
Ractive
Next-generation DOM manipulation
JsRender
A light-weight but powerful templating engine, highly extensible, without DOM or jQuery dependency.
Machina.js
js ex machina - finite state machines in JavaScript