History.js
History.js gracefully supports the HTML5 History/State APIs (pushState, replaceState, onPopState) in all browsers. Including continued support for data, titles, replaceState. Supports jQuery, MooTools and Prototype. For HTML5 browsers this means that you can modify the URL directly, without needing to use hashes anymore. For HTML4 browsers it will revert back to using the old onhashchange functionality.
Grapnel.js
A simple, lightweight library making it easy to create routes or run events based on a specific URL hashtag.
Csso
CSS-optimizer
Webshim
Webshims Lib is a modular capability-based polyfill-loading library
Pilot
Pilot — multifunction JavaScript router.
Routie
a tiny javascript hash router
Is.js
Micro check library
Jwerty
Awesome handling of keyboard events
Backbone Deep Model
Improved support for models with nested attributes.
Page.js
Micro client-side router inspired by the Express router (~1200 bytes)
Rx Js
The Reactive Extensions for JavaScript
Raven Js
JavaScript client for Sentry
Mediator.js
An implementation of the mediator pattern for asynchronous events in Javascript
Fast.js
Faster user-land reimplementations for several common builtin native JavaScript functions.
Lazy.js
Like underscore.js, but lazier
Refluxjs
A simple library for uni-directional dataflow application architecture inspired by ReactJS Flux
Contra
Asynchronous flow control with a functional taste to it