Rando.js
The world's easiest, most powerful random function.
Prototype
Prototype JavaScript framework
Gator
Event delegation in Javascript
Phantomjs
Scriptable Headless WebKit
Dragula
:ok_hand: Drag and drop so simple it hurts
Bespoke.js
DIY Presentation Micro-Framework
Fastdom
Eliminates layout thrashing by batching DOM read/write operations
Responsive Comments
A client-side solution to conditional loading.
Voyeur.js
Voyeur is a tiny (1.2kb) Javascript library that lets you traverse and manipulate the DOM the way it should have been.
Mag.js
MagJS - Modular Application Glue
Tapestry5 jQuery
Tapestry 5 jQuery integration. Fully replace Prototype and Scriptaculous with jQuery with as less as possible compatibility issues
Shuffle
jQuery Shuffle Plugin
State
Hierarchical finite state machine for TypeScript and JavaScript
Minified.js
Replace jQuery or MooTools with a <4kB Library
Tippyjs
Highly customizable vanilla JS tooltip/popover library
jScrollPane
Pretty, customisable, cross browser replacement scrollbars
Prefixfree
Break free from CSS prefix hell!