Gridsome is a free and open source Vue.js-powered framework for building modern websites & apps that are super fast.
SpriteJS is a lightweight 2D canvas rendering engine for modern browsers. Manipulate the sprites in canvas as you do with the DOM elements.
SpriteJS can be used with D3.js, Proton and Matter-js.
DOMtastic is a small, fast, and modular DOM & Event library for modern browsers. Same familiar API as jQuery.
Works great stand-alone or paired up with e.g. Backbone or Angular.
Quill is a modern rich text editor built for compatibility and extensibility. It's a free, open source WYSIWYG editor built for the modern web.
howler.js is an audio library for the modern web. It defaults to Web Audio API and falls back to HTML5 Audio.