A better way to use localStorage and sessionStorage
Small, fast, awesome. The only ES5-ish set of polyfills (shims) you can mix-and-match because they're individual AMD modules.
CSS4 parent selector based on jQuery
Tired of adding prefix for each broswer when it comes to the new css3 attributes?
JS string formatter that supports objects, currency, date/time, decimals, and more supports easy extension and garbage collection ... goes far beyond sprintf approach.
Tiny polyfill for the placeholder form element attribute. Requires Prototype.js.
Legacy support for the CSS3 Flexible Box Model
A lightweight engine that allows you to hitch new capabilities to the browser (prollyfill).
Allows for automatic Image fallbacks for browsers that can't handle SVGs
A fast & lightweight polyfill for min/max-width CSS3 Media Queries (for IE 6-8, and more)
An Asynchronous Conditional Resource Loader
This script is the defacto way to enable use of HTML5 sectioning elements in legacy Internet Explorer.