This plugin is an entire gwt rewritte of the JQuery-ui draggable plugin
The Draggable plugin enables draggable functionality on any DOM element and GWT widget (it makes the selected element draggable by mouse).
More information available at : http://code.google.com/p/gwtquery-plugins/wiki/DraggablePluginGettingStarted
Examples are available here
Original author of this plugin: Julien Dramaix