Fast.js
Faster user-land reimplementations for several common builtin native JavaScript functions.
Pixel Craft
A Pixel Art Editor
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.
Mobx
Simple, scalable state management.
ifvisible.js
Checks if the current page is visible or not
Px Loader
PxLoader is a simple JavasScript library for creating preloaders and resource downloaders for HTML5 apps.
Routie
a tiny javascript hash router
Refluxjs
A simple library for uni-directional dataflow application architecture inspired by ReactJS Flux
Next.js
Next.js is a lightweight framework for static and server‑rendered applications.
Canjs
Can do JS, better, faster, easier.
Theory
Abstraction layer for cross platform JavaScript.