Page.js
Micro client-side router inspired by the Express router (~1200 bytes)
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.
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
Lodash
An alternative to Underscore.js, delivering consistency, customization, performance, and extra features.
Modernizr
Modernizr is a JavaScript library that detects HTML5 and CSS3 features in the user’s browser.
Mousetrap
Simple library for handling keyboard shortcuts in Javascript
Platform.js
A platform detection library that works on nearly all JavaScript platforms.
Humane.js
A simple, modern, browser notification system
Tweet
put twitter on your website with tweet, an unobtrusive javascript plugin for jquery
Twitterlib
Twitter JavaScript API library
Use.js
An AMD/RequireJS plugin for consuming incompatible JavaScript files.
Visibility.js
Visibility.js allows you to determine whether your web page is visible to a user, is hidden in background tab or is prerendering. It allows you to use the page visibility state in JavaScript logic and improve browser performance by disabling unnecessary timers and AJAX requests, or improve user interface experience (for example, by stopping video playback or slideshow when user switches to another browser tab).
Gas
Google Analytics on Steroids. A Google Analytics implementation with more power features.
Eve.js
A <3kb JavaScript file providing three simple methods to organize code into CSS namespaces which magically restrict code to the current context, allowing for dramatic reductions to code size and development time.