Some handy and helpful commands for jQuery lovers authored by Brandon Aaron which includes following:

batch
Batch is a jQuery plugin that gives you the ability to batch the results of any jQuery method or plugin into an Array.

bgiframe
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A jQuery plugin that helps ease the pain when having to deal with IE z-index issues.

copyevents
A jQuery plugin that provides method for copying events from one element to another.
countable
A jQuery plugin that provides an unobtrusive input and textarea character counter.

each_slice
jQuery plugin that lets you iterate the given function for each slice of elements

expandable
A jQuery plugin that auto-expands textareas to fit the contents as a user types.

getfeed
A jQuery plugin wrapper for using the Google feeds API.
getscrollbarwidth

A jQuery plugin to retrieve the width of a system scrollbar.

gradient
A jQuery plugin that adds a dynamically created configurable gradient to the background of an element without the use of images.

mousewheel
A jQuery plugin that adds cross-browser mouse wheel support.

outerhtml
A jQuery plugin for getting the outerHTML of an element.

overlabel
A jQuery plugin to help implement the over label technique described in Making Compact Forms More Accessible by Mike Brittain on ALA.

scrollwindow
A scroll window plugin for jQuery.

spellcheck
A jQuery plugin that adds spellcheck support to inputs using the Google spell checker API.

swap
A jQuery plugin to swap elements within the DOM.

livequery
Live Query utilizes the power of jQuery selectors by binding events or firing callbacks for matched elements auto-magically, even after the page has been loaded and the DOM updated.

viewable
A jQuery plugin that allows you to know when an element is in view and what percentage of the element is viewable.

Virtual DOM Events
A collection of jQuery special events that provide more precision over normal DOM events. Includes mouserest, mouseremainover, mouseremainup, mouseremaindown, mouseremainout, keyremaindown, keyremainup, remainfocused, and remainblurred.