Slidr.js is a simple, lightweight javascript library for adding slide transitions to your page. No dependencies required.
A template for a split layout with two sides. When clicking on a half in the initial view, the layout moves into the respective direction.
Split layout template
Here is an awesome jQuery plugin for creating an Apple-like one page scroller website (iPhone 5S website) with One Page Scroll plugin.
One page scroll – jQuery plugin
Pace.js is a new plugin for easily showing fancy progress bars while is your website is loading. Pace will monitor your ajax requests, etc.
Pace.js – Progress bars for websites
iTunes-style coverflow made with CSS3 and some lines of Javascript. A CSS snippet coded by Hjörtur Hilmarsson.
Cowerflow style with CSS3 and Javascript
Justin Windle has created a 3D dropdown menu with awesome animations with CSS3 and just few lines of javascript.