Sencha (previously known as Ext JS) has released Sencha Touch, a HTML5 Mobile Application Framework. which allows you to develop web applications that look and feel native on Apple iOS and Google Android touchscreen devices.
It makes use of HTML5 for delivering audio/video or localStorage and CSS3 for maximum styling like rounded corners, background gradients, and shadows.
The code created is resolution independent. It uses a method which allows developers to change the overall scale of their interfaces on the fly with no pixellation.
Sencha Touch has a powerful animation system that makes flexible animations between screens and views possible.
Slide, pop, and fade animations are included with the library, each with a robust set of options to change attributes like direction and masking style.
And, as they are created with CSS, building custom animations is a joy.
Also, it includes a set of common icons for using them in toolbars and tab bars.