Augment.js
Modern JavaScript in your IE
Char Funk
a Unicode character utility for JavaScript
Es6 Shim
ECMAScript 6 (Harmony) compatibility shims for legacy JavaScript engines
CSS3 Pie
A behavior for Internet Explorer allowing it to recognize and render various CSS3 box decoration properties
Args.js
Create javascript functions with optional, default, grouped and named parameters.
Css3 Finalize
Tired of adding prefix for each broswer when it comes to the new css3 attributes?
Sugar
A Javascript library for working with native objects.
Typecast.js
Typecast.js :: Solving the simple problems
ES5 Shims
ECMAScript 5 compatibility shims for legacy JavaScript engines
Core Lib
A port of the Ruby 1.9.3 corelib to coffeescript/javascript/node that conforms to rubyspec.org.
Datejs
Datejs is an open-source JavaScript Date Library.
Ratio.js
Rational numbers for Javascript
Timezone Js
Timezone-enabled JavaScript Date object. Uses Olson zoneinfo files for timezone data.
Object.observe
Object.observe polyfill/shim trying to be compliant
Poly
Small, fast, awesome. The only ES5-ish set of polyfills (shims) you can mix-and-match because they're individual AMD modules.
Big.js
A small, fast JavaScript library for arbitrary-precision decimal arithmetic.
Length.js
📏 JavaScript library for length units conversion.