jsTree is a javascript based, cross browser tree component. It is packaged as a jQuery plugin

Requeriments:jQuery Framework
License: MIT, GNU , and GPL License

Proto.Menu is a simple and lightweight prototype-based solution for context menu functionality on your page.

Features:

• Lightweight: ~3 KB (~2 KB minified)
• Unobtrusive: Plays nice with JS turned off, uses its own namespace
• Cross-browser: Full A-Graded browsers support (Opera is supported through Ctrl + Left Click)
• Fully customizable: Menu styling can (and is intended to) be easily defined in external stylesheet, supports image-based themes
• Fast: Menu container is rendered on page load, and only changes position when rendered (on click event)
• Thoroughly tested: Features extensive set of unit tests to ensure expected behavior

Requeriments:prototype Framework
License: GPL License

Menu Background Image Animations can change the position of the background image felt to be the best approach to creating the type of effect we’re looking for

The animation needs to run when the user moves their mouse over and out of the navigation. The key thing to note is that any animation is stopped before attempting to animate again. This avoids animations queuing up from repeatedly moving the mouse in and out of the element.

Requeriments:jQuery Framework
License: MIT, and GPL License

Features:
* It allows onClick event keeps selected item open.
* Click open item to close.
* Specify a function for the onClick event.
* Auto open when the page loads.

Requeriments:Mootools Framework
License: License Free

Mif.Menu supports multi-level and key navigation as well. There are ART style and shadow style context menu for you to choose from.

Requeriments:Mootools Framework
License: Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License

The iPod Drilldown and Flyout Styles Menu System can be used to create a simple dropdown menu for a single list of options, a flyout menu for a smaller hierarchical list of options where child menus are displayed next to the parent menu on mouseover, and two variations on the iPod style, one with a back button and another with a linked breadcrumb to let users easily traverse back up the hierarchy.

Requeriments:jQuery Framework
License: MIT and GPL License

BySlideMenu is a plugin for Mootools which allow you to easily create a beautiful accordion menu (sliding menu) on any element you want (ul/li, div, p …) using images and/or text.
Features
* Works horizontally or vertically.
* Automatic size – The container width/height can be adjusted automatically.
* Menu is expandable by mouseover or by click, as you want.
* Menu can be pinned or not, by mouseover or click, you choose.
* A default index can be defined.
* Can be used with any elements (ul/li, div, p…)
* Overflow support.

Requeriments:Mootools Framework
License: MIT License

I love Mac apps, especially for their attention to detail. CoreAnimation makes it so easy to create useful and eye-pleasing effects, like the one in this video. Quicksand aims at providing a similar experience for users on the web.
At the very basic level, Quicksand replaces one collection of items with another. All you need to do is provide those two sets of items. You can do it in a couple of ways:

1. Use plain HTML, like an unordered list.
2. Download data by an Ajax call
3. Transform HTML items by JavaScript (for example, sort them differently)

Requeriments:jQuery Framework
License: MIT and GPL2 License

BubbleUP jQuery Plugin is a fun and easy plugin to get you started in jQuery. The effect is a nice starting point for learning the basics and many of the steps involved in creating other more intricate plugins you will make in the future.
With BubbleUP, images in a list will enlarge with a smooth animation when you move your mouse over it. Then, if you move the mouse out, it will reset to the original size with the same smooth animation. It has been tested on IE 7, Opera 10, Firefox 3.5, Safari 4, and Chrome 5 Beta.

Requeriments:jQuery Framework
License: License Free

SliderNav is a JQuery plugin that lets you add dynamic, sliding content using a vertical navigation bar (index). It is made mainly for alphabetical listings but can be used with anything, though longer words can look a bit awkward. The plugin automatically adds the navigation and sets the height for the object based on how tall the navigation is, in order to make sure users have access to the entire list. I also used the overflow: auto; property for the actual content so you can use your mousewheel to scroll through the content as well.
The plugin has been tested (and works fine) on Firefox 3, Chrome 5, IE7, Safari 4 and Opera 10.

Requeriments:jQuery Framework
License: MIT, BSD, and GPL License