Pluin for Category sensitive sub menus

I would like to find a plugin for a submenu that would go in the widget area and would change depending on which category was selected. At the moment I have a sub menu that is getting very large and it has a tree structure. What I want is to only show the first level. When one of the menu items is selected it displays posts with the defined category. I would like another submenu to appear with children of that category. If one of these items is selected then I would like the submenu to change to show children of the child category. Does anyone know if such a plugin exists?