Sherlock
Natural-language event parser for Javascript
Page.js
Micro client-side router inspired by the Express router (~1200 bytes)
Simplate
A simple, but powerful, templating engine for JavaScript.
Hermes.js
Message and Error logger implementation
Grapnel.js
A simple, lightweight library making it easy to create routes or run events based on a specific URL hashtag.
Enyo
A JavaScript application framework emphasizing modularity and encapsulation
Backbone Marionette
Make your Backbone.js apps dance with a composite application architecture!
Stapes
a (really) tiny Javascript MVC microframework
Spine
Lightweight MVC library for building JavaScript applications
Simplecart
A simple javascript shopping cart that easily integrates with your current website.
Script.js
Asyncronous JavaScript loader and dependency manager
Sammy
Sammy is a tiny javascript framework built on top of jQuery, It's RESTful Evented Javascript.
JS Signals
Custom Event/Messaging system for JavaScript inspired by AS3-Signals
JSON Editor Online
A web-based tool to view, edit and format JSON
jStorage
jStorage is a simple key/value database to store data on browser side. As a bonus it is also a local pubsub platform to sync data between tabs/windows
Knockout
Knockout makes it easier to create rich, responsive UIs with JavaScript
LABjs
Loading And Blocking JavaScript: On-demand parallel loader for JavaScript with execution order dependencies