The big news this week both came from Microsoft with the open sourcing of WinJS and TypeScript reaching 1.0.

WinJS is a set of open-source JavaScript toolkits from Microsoft containing sets of UI controls and components.
WinJS

TypeScript 1.0 is available as part of Visual Studio 2013 and Visual Studio Web Express 2013 Spring Update, as an npm package, and as source.
Announcing TypeScript 1.0

QuoJS is a micro JavaScript library designed for mobile including touch events/gestures, DOM manipution and more.
QuoJS - Micro JavaScript Library

Pixi.js 1.5.2 includes CacheAsBitmap and GenerateTexture as well a ton of other updates.
PIxi.js 1.5.2 webGL and Canvas 2d renderer

Mithril is a JavaScript MVC framework for web applications with no dependencies and a simple API.
Mithril

Route is a Node module where you pass a list of cities and get the shortest route and the distance corresponding to that route.
shortest-route

PositionCalculator can calculate the position of an element relative to another element or event.
PositionCalculator

Haste is a dialect of the Haskell that compiles to JavaScript.
Haste