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