Zoom.js
zoom in on any element in the DOM
Mercury
A truly modular frontend framework
jQuery.nicescroll
nicescroll plugin for jquery - scrollbars like iphone/ipad
Do Mtastic
Small & fast DOM and event library for modern browsers.
Shuffle
jQuery Shuffle Plugin
Polymer
Leverage the future of the web platform today.
Interact.js
Drag and drop, resizing and multi-touch gestures with inertia and snapping for modern browsers (and also IE8+)
Kimbo.js
An ECMAScript 5 only-compatible JavaScript library.
Phantomjs
Scriptable Headless WebKit
Fastdom
Eliminates layout thrashing by batching DOM read/write operations
Wow
Reveal CSS animation as you scroll down a page
Veinjs
Injects CSS into the document (it's a perfectly legal procedure)
jQuery Evergreen
Small & fast DOM and event library for modern browsers.
Responsive Comments
A client-side solution to conditional loading.
Bespoke.js
DIY Presentation Micro-Framework
Bonzo
library agnostic, extensible DOM utility
Porthole
A proxy to safely communicate to cross-domain iframes in javascript