The BDC DrillDown Menu is a compact, hierarchical menu implemented as a jQuery plugin. A drilldown menu takes up constant space like an accordian menu but offers the deep hierarchy of a flyout menu at the same time. The BDC DrillDown Menu turns a standard HTML list into a dynamic JavaScript drilldown menu that maintains a small profile no matter how deep the hierarchy it controls. This is quite similar (though with more features) to the menu used in the iPod.
