This script is the defacto way to enable use of HTML5 sectioning elements in legacy Internet Explorer.
CSS4 parent selector based on jQuery
A fast & lightweight polyfill for min/max-width CSS3 Media Queries (for IE 6-8, and more)
A lightweight engine that allows you to hitch new capabilities to the browser (prollyfill).
Legacy support for the CSS3 Flexible Box Model
Tiny polyfill for the placeholder form element attribute. Requires Prototype.js.
An Asynchronous Conditional Resource Loader
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?
A better way to use localStorage and sessionStorage
Allows for automatic Image fallbacks for browsers that can't handle SVGs