Collect.js is a convenient and dependency free wrapper for working with arrays and objects.
LineProgressbar is a lightweight and customisable jQuery progressbar plugin. It's under MIT licence.
Store.js is a localStorage wrapper for all browsers without using cookies or flash. Uses localStorage, globalStorage, and userData behavior under the hood.
jQuery.appear is a jQuery plugin for tracking element's appearance in browser viewport. It's licensed under MIT license.
jqGifPreview is a jQuery plugin tocreate GIF preview just like Facebook. This plugin use first frame of GIF image as preview image.
A tutorial about creating a simple jQuery Accordion with unlimited nesting.