jsPerf aims to provide an easy way to create and share test cases, comparing the performance of different JavaScript snippets by running benchmarks.

Undum is a tool for writing hypertext interactive fiction. It has some unique features and a visual design that encourages narrative games.

PhoneGap is an open source development framework for building cross-platform mobile apps. Build apps in HTML and JavaScript and still take advantage of core features in iPhone/iTouch, iPad, Google Android, Palm, Symbian and Blackberry SDKs

WebTest has an easy syntax with steps having meaningful names that can be understood even when you don't know WebTest. Additionally, the recorder allows you to quickly generate a first draft of your tests that you can adapt and refactor to build robust tests suites. Don't forget: capture/replay is the least cost-effective way of automating test cases!

Chroma-Hash allows you to quickly compare the contents of two secure text fields. It’s common for a signup flow to ask you to type your password twice (to make sure you didn’t mistype it). With this visualization, a user can instantly check to see if what she typed was the same each time, without having to submit the form.

Caja allows websites to safely embed DHTML web applications from third parties, and enables rich interaction between the embedding page and the embedded applications. It uses an object-capability security model to allow for a wide range of flexible security policies, so that the containing page can effectively control the embedded applications' use of user data and to allow gadgets to prevent interference between gadgets' UI elements.

Unveil is a data exploration and visualization toolkit that utilizes data-driven software design.

It features generic data abstraction through Collections, a unified interface for developing pluggable visualizations, and a Scenegraph implementation that simplifies the usage of the the HTML 5 Canvas API .

Although shipping with it's own little graphic library, the Scene API, Unveil.js is designed to be used with any other visualization library. So in the first place, it suggests a different approach on how you deal with domain data in a visualization scenario.

A simple in-process key/value document store for node.js. nStore uses a safe append-only data format for quick inserts, updates, and deletes. Also a index of all documents and their exact location on the disk is stored in in memory for fast reads of any document. This append-only file format means that you can do online backups of the datastore using simple tools like rsync. The file is always in a consistent state.

Underscore provides 60-odd functions that support both the usual functional suspects: map, select, invoke — as well as more specialized helpers: function binding, javascript templating, deep equality testing, and so on. It delegates to built-in functions, if present, so modern browsers will use the native implementations of forEach, map, reduce, filter, every, some and indexOf.

JSonduit is a service that can turn practically anything on the web into a JSON feed that any website or mobile app can consume. A JSON conduit, if you will.

Feeds are created from one or more source URLs and a custom transform, written in JavaScript, that can manipulate the data before the feed is served.

JSonduit also provides a hosting service for web widgets so that any site can easily display JSonduit feeds. In fact, the recent/popular lists you see below are widgets served by the JSonduit service; all done in a couple of lines of JavaScript (go ahead, view the page source!).