jQuery UI Library For Desktop-Like Apps – w2ui
w2ui is a jQuery UI library with many widgets for creating desktop-like and data-driven web applications.
The library comes as plugins for each widget so that you can choose which ones to use.
It consists of the following widgets: layout, sidebar, toolbar, grid, popup, tabs, forms and field controls.
They all play well with each other, make use of HTML5-CSS3 and have powerful APIs for controlling all the aspects of them.
w2ui is very well-documented, has lots of demos to play with and it is being improved regularly.