Typeahead.js
A fast and fully-featured autocomplete library
Round Slider
roundSlider - A free jQuery plugin
Infinity
UITableViews for the web.
Hide Seek
A simple, mobile-friendly, yet customizable quick/live search jQuery plugin.
Timelined
A customizable CSS-only vertical timeline
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!
Multiple.js
Sharing background across multiple elements using CSS
Droptiles
Droptiles is a "Windows 8 Start" like Metro-style Web 2.0 Dashboard. It compromises of Live Tiles. Tiles are mini apps that can fetch data from external sources. Clicking on a tile launches the full application.
iCheck
Highly customizable checkboxes and radio buttons
Joyride
jQuery feature tour plugin.
Expounder
A library for explaining things in HTML.
Dragscroll
tiny library for drag-n-drop scrolling style
Itemslide.github.io
A simple and beautiful JavaScript touch carousel
Ng Morphing Modal
Angular Morphing Modal
Toolbar
A tooltip style toolbar jQuery plugin
Background Check
Automatically switch to a darker or a lighter version of an element depending on the brightness of images behind it.
Select2
Select2 is a jQuery based replacement for select boxes. It supports searching, remote data sets, and infinite scrolling of results.