haXe is an open source & multiplatform programming language.
A code written with haXe can be compiled to JavaScript, Flash (AS2 & AS3), PHP and NekoVM which is all the idea behind the project: "let the developer choose the best platform to do a given job".

haXe has installers for Windows, OSX & Linux and the platform is well-documented.
For writing haXe code, plugins for several popular editors can be found here.
Requirements: No Requirements
Compatibility: Windows, OSX & Linux
js-hotkeys is a jQuery plugin which enables you to create keyboard triggered events.
Update: The plugin is based on shortcut.js. You may want to use this for not being restricted with jQuery.
This is a very nice feature if you want to provide users more browsing flexibility. And also, it can be used in JavaScript testing environments like triggering a test function by clicking CTRL + t.

A simple usage of the plugin is:
$.hotkeys.add('Ctrl+a',function(){/*DO YOUR DUTY*/});
$.hotkeys.remove(’Ctrl+a’);
A demo of this jQuery keyboard control plugin can be found here.
Requirements: jQuery
Compatibility: All Major Browsers (some handicaps are mentioned at the product website)
woork presents a nice MooTools news ticker, which scrolls vertically, similar to the one in Newsvine.

Content is currently hard-coded inside the HTML within li elements. There is also an information provided for how to get the content dynamically from a database.
Speed & delay of the slide effect can be configured within the code.
Requirements: MooTools
Compatibility: All Major Browsers
Spacegallery is a very simple but nice image gallery built with jQuery.
It is a static gallery where images are hardcoded in the HTML and presented with a beautiful grow - fade out effect.

How to use?
After inserting the JS & CSS files into your webpages, create a div element with images inside like:
<div id="myGallery" class="spacegallery">
<img src="images/bw3.jpg" alt="BW" />
<img src="images/lights3.jpg" alt="Lights" />
</div>
And call the gallery:
$('#myGallery').spacegallery({loadingClass: 'loading'});
You can also configure the perspective, border & animation duration.
Requirements: jQuery
Compatibility: All Major Browsers
jqPuzzle is a jQuery plugin which enables you to create sliding puzzles from any image.
The created JavaScript puzzle can have the shuffle & solution options besides the moves made & seconds played.

jqPuzzle is highly configurable as the options in the interface can be enabled/disabled, number of rows & columns of the puzzle to be created can be defined & more.
How to use?
After inserting the jquery.jqpuzzle.js & jquery.jqpuzzle.css files to your webpage, simply give the class="jqPuzzle" to any image. That’s all.
Requirements: jQuery 1.2.1+
Compatibility: All Major Browsers
CRIR is a combination of JavaScript & CSS that enables you to create custom checkbox and radio buttons.
Note: Seems like the website is currently down. Click here for the cached version from Yahoo.

Behind the scenes, CRIR does it with a visual trick by hiding the original form elements (but transferring any values to them) and replacing them with images.
Requirements: No Requirements
Compatibility: All Majosr Browsers
jQuery Sparklines is a plugin for creating sparklines on the fly.
What is a sparkline:

They are data-intense, design-simple, word-sized graphics that are commonly used in market, stock activity and can be implemented anywhere (via Wikipedia).
This plugin supports:
- Line graphs
- Bar charts
- And, tristate charts

jQuery Sparklines plugin can be used to create graphs from data inside the HTML or via JavaScript. Almost every variable of it can be customized including colors, size & chart type.
Requirements: jQuery
Compatibility: All Major Browsers
JavaScript Image Effects is a library that you can instantly create effects like rotate, blur, emboss & more.

Using such a library is very functional in situations where you may need to add an effect to lots of images, need to provide an interface to the users for creating effects & so.
How to use?
After inserting the imagefx.js file into your webpage, you have 2 options:
<script type="text/javascript" >
jsImageFX.doImage(document.getElementById("myimage"), "blur");
</script>
or
<img src="image.jpg" imagefx="blur" />
where both are very easy to apply.
Every image effect is not available in every browser and a comprehensive browser compatibility chart can be found in the website
Requirements: No Requirements
Compatibility: Browser compatibility chart is provided at the website.
jqZoom is a jQuery plugin which enables images to be zoomed.
This is an easy-to-implement plugin which is very handy, specially, in e-commerce projects & galleries.

How it works?
This jQuery zoom plugin simply requires that "jqzoom" class to be added to images other that including the JS file and calling the main function once. And that’s it.
You can also configure it to mention the width-height of the zoom div and its position.
Requirements: jQuery
Compatibility: All Major Browsers
Tipmage is a JavaScript class for creating tooltips / notes over images similar to Facebook image tagging.
In order to create a tooltip, you simply double click any area on the image and the interface appears.

It works in 2 modes:
- Normal: which only shows the tooltip when hovered.
- Edit: which also allows you to edit the tooltip
Tipmage supports the use of special callback functions for editing of a tooltip (like Ajax calls to access a database) & the editing interface can be updated from a CSS file.
Requirements: No Requirements
Compatibility: All Major Browsers