jQuery

cyclotron is a simple jQuery plugin for dragging 360° panoramas (cylindrical projection) and other seamlessly looping images around.    

JqTree is a tree widget for jQuery.   JqTree - Features: Create a tree from JSON data Drag and drop Works on ie7+, firefox 3.6+, chrome and safari Written in Coffeescript    

Gridly is a jQuery plugin to enable dragging and dropping as well as resizing on a grid.    

Mosaiqy is a jQuery plugin to organize and show image thumbnails and zoom, easy to integrate also with Flickr, Instagram, Panoramio and other.  Thumbnails are arranged in a grid and each row and column could be randomically moved, sliding in every direction and showing other thumbnails available. Image data is described as a regular JSON object.  And all expensive animations are taken over by your GPU on recent browsers using CSS3 transitions, minimizing the CPU overhead.     

Picbox is a lightweight javascript image viewer based on the excellent Slimbox by Christophe Beyls, and available using either the Mootools or jQuery frameworks. It features automatic resizing and zooming of large images, allowing them to fit in the browser or be viewed at full size.    

Tipsy is a jQuery plugin for creating a Facebook-like tooltips effect based on an anchor tag's title attribute.    

WikiUp is a jQuery plugin which gets Wikipedia descriptions in tooltips.    

FullCalendar is a jQuery plugin that provides a full-sized, drag & drop calendar. It uses AJAX to fetch events on-the-fly for each month and is easily configured to use your own feed format (an extension is provided for Google Calendar). It is visually customizable and exposes hooks for user-triggered events (like clicking or dragging an event).     

sBubble is a jQuery tooltip plugin which is totally based on CSS3 for shapes and animations. There are no images used and no jQuery code used for animation. Plus some color themes are also provided.    

Overscroll is a jQuery plug-in that mimics the iphone/ipad scrolling experience in a browser. The plug-in adds a draggable drift to overflowed DOM elements as well as a set of fading 'thumbs'. OverScroll runs best on Safari 5+, Chrome 5+, and Firefox 3+ but should run just fine on most modern browsers.