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