Persist State
jQuery Ui widget that will transparently save the state of checkboxes, inputs, selects, etc in localStorage, restoring these on the user's next visit to the page.
Fragment.js
A tiny tool for easily loading html fragments and templates
Elements
E+lements is a minimal DOM Library for the prime framework.
Porthole
A proxy to safely communicate to cross-domain iframes in javascript
jQuery.lazy
A lightweight, fast, feature-rich, powerful and highly configurable delayed content, image and background lazy loading plugin for jQuery & Zepto.
Double
jQuery plugin for hiring doubles
jScrollPane
Pretty, customisable, cross browser replacement scrollbars
Responsive Comments
A client-side solution to conditional loading.
Phantomjs
Scriptable Headless WebKit
Viewport
Gets the dimensions of the Viewport and beyond.
Eqcss
EQCSS is a plugin that introduces Element Queries, Scoped CSS, a Parent selector, and responsive JavaScript to all browsers IE8 and up
jQuery Evergreen
Small & fast DOM and event library for modern browsers.
Node List.js
NodeList implementation/library - Use the Native DOM APIs as easily as jQuery
Veinjs
Injects CSS into the document (it's a perfectly legal procedure)
Kimbo.js
An ECMAScript 5 only-compatible JavaScript library.
Tether
A positioning engine to make overlays, tooltips and dropdowns better #hubspot-open-source
Resize Observer
Polyfills the ResizeObserver API.