Underscore
JavaScript's utility _ belt
Knockout Projections
Knockout.js observable arrays get smarter
Davis.js
RESTful degradable JavaScript routing using pushState
JayData
JayData is a unified data access library for JavaScript to CRUD data from different sources like WebSQL/SQLite, IndexedDB, MongoDb, ASP.NET WebAPI, OData, HTML5 localStorage, Facebook or YQL. The library can be integrated with KendoUI, Knockout.js, Handlebars.js or Sencha Touch 2 and can be used on Node.js as well.
Modules Webmake
Bundle CommonJS/Node.js modules for web browser
Fast.js
Faster user-land reimplementations for several common builtin native JavaScript functions.
Pegasus
Load data while still loading other scripts and display data faster in jQuery, Backbone, Angular, ... apps
Cram
Simple AMD and CommonJS module bundler.
Bootstrap Ajax
A library for adding declarative ajax functionality to your website
Backbone Deep Model
Improved support for models with nested attributes.
Sentry
Sentry is a realtime error logging and aggregation platform
Platform.js
A platform detection library that works on nearly all JavaScript platforms.
Amplify
AmplifyJS is a set of components for data management and application communication.
ifvisible.js
Checks if the current page is visible or not
Routie
a tiny javascript hash router
Refluxjs
A simple library for uni-directional dataflow application architecture inspired by ReactJS Flux
Theory
Abstraction layer for cross platform JavaScript.