Browser Sync
Keep multiple browsers & devices in sync when building websites. http://browsersync.io
Assemble
Static site generator for Node.js, Grunt.js, and Yeoman (and soon, Gulp), using the Handlebars template engine. Used by Zurb Foundation, Zurb Ink, H5BP/Effeckt, Less.js / lesscss.org, Topcoat, Web Experience Toolkit, and hundreds of other projects to build sites, themes, components, documentation, blogs and gh-pages. Pull requests welcome, stars appreciated!
Yepnope.js
An Asynchronous Conditional Resource Loader
Crafty
Crafty is a JavaScript game library that can help you create games in a structured way.
Lucia
🙋♀️ 3kb library for tiny web apps
Express
Sinatra inspired web development framework for node.js -- insanely fast, flexible, and simple
Code Blast Codemirror
Particles blasts while typing in Codemirror
Darken
🌑 Dark mode made easy
Open Location Code
Open Location Codes are short, generated codes that can be used like street addresses, for places where street addresses don't exist.
Responsive Elements
Responsive elements makes it possible for any element to adapt and respond to the area they occupy. It's a tiny javascript library that you can drop into your projects today.
Oboe.js
A fresh approach to AJAX that speeds up web applications. Progressive JSON parser with an easy interface so you can use the objects before the http response completes.
Layzr.js
A small, fast, modern, and dependency-free library for lazy loading.
Form
jQuery Form Plugin
Speakingurl
Generate of so called "static" or "nice-looking" or "slug" or "SpeakingURL" from a string.
Ratchet
Prototype iPhone apps with simple HTML, CSS, and JS components.
Prism
Lightweight, robust, elegant syntax highlighting. A spin-off project from Dabblet.
No Ui Slider
noUiSlider is a lightweight JavaScript range slider library. It offers a wide selection of options and settings, and is compatible with a ton of (touch) devices, including those running iOS, Android, Windows 8 and Windows Phone 8.