Grunt
Grunt: The JavaScript Task Runner
Fastclick
Polyfill to remove click delays on browsers with touch UIs
Scroll Reveal.js
Declarative on-scroll reveal animations.
Signal R
Incredibly simple real-time web for .NET
Scroll Magic
The jQuery plugin for magical scroll interactions.
Remark
A simple, in-browser, markdown-driven slideshow tool.
Nprogress
For slim progress bars like on YouTube, Medium, etc
Testcafe
A Node.js tool to automate end-to-end web testing.
Bower
A package manager for the web, created at Twitter
Jszip
Create, read and edit .zip files with Javascript
Marko
Marko template engine
Mediaelement
HTML5 <audio> or <video> player with Flash and Silverlight shims that mimics the HTML5 MediaElement API, enabling a consistent UI in all browsers.
Skrollr
Stand-alone parallax scrolling library for mobile (Android + iOS) and desktop. No jQuery. Just plain JavaScript (and some love).
Store.js
localStorage wrapper for all browsers without using cookies or flash. Uses localStorage, globalStorage, and userData behavior under the hood
Robotjs
Node.js Desktop Automation.
Pdfmake
Client/server side PDF printing in pure JavaScript
RequireJS
A file and module loader for JavaScript