jDashboard is a jQuery Plugin that gives you an easy way to create a dynamic widget area. The widgets can easily be re-arranged and collapsed/expanded, and the layout is saved either in a MySQL database, or with HTML5 local storage (falling back to using cookies) so your users don't need to start over when they come back to their dashboard.
In live preview, you may need to remove the frame(top left link) for the cookies to work.