jQuery jKit
A very easy to use, cross platform, jQuery based UI toolkit, that's still small in size, has the features you need, and doesn't get in your way of doing things!
Fartscroll.js
You want fart noises as you scroll? We've got you covered.
Uptodate
Keep your timestamps up to date
jQuery Snipe
jQuery plugin to add a sniper-lens-style zoom on images
jQuery Impromptu
An extention to help provide a more pleasant way to spontaneously prompt a user for input.
Avgrund
Avgrund is a jQuery plugin with new modal concept for popups
jPanelMenu
A jQuery plugin that creates a paneled-style menu (like the type seen in the mobile versions of Facebook and Google, as well as in many native iPhone applications).
Bootstrap Switch
unofficial bootstrap switch
Hook.js
Pull to refresh. For the web.
Opentip
An open source javascript tooltip based on the protoype framework.
jVectorMap
Show interactive vector maps on the web.
jQuery Knob
Nice, downward compatible, touchable, jQuery dial
Filtrify
Beautiful advanced tag filtering with HTML5 and jQuery
jPages
Client side pagination with jQuery and CSS3
Typeahead.js
A fast and fully-featured autocomplete library
FullCalendar
Full-sized drag & drop event calendar (jQuery plugin)
Tiles.js
A simple JavaScript library for creating tile-based edge-to-edge layouts. Built on jQuery.