There is a plugin in the jQuery plugins repository, http://plugins.jquery.com/project/multidraggable, that does this for jQuery 1.3.x.
When I use it in 1.4.x (and jQuery UI 1.8.x), I am able to select multiple elements, but when I drag, only one element is dragged.
Can anyone help explain how I could get this working? Not sure if this is outside the realm of stack overflow, if so, my apologies.