$(function(){
    var menu = $("#nav");

    menu.find("ul.sf-menu")
        .superfish({
            delay:         0,
            speed:         'fast',
            autoArrows:    false,
            dropShadows:   false,
            onHide:        function(){
                if (this.parent().is('.sfPersist')) {
                    this.show().css('visibility','visible').parent().addClass('sfHover');
                }
            }
        })
        .find('li > ul > li').click(function(){
            // hide previously persistent children (LOL that just sounds wrong)
            menu.find('.sfPersist')
                .removeClass('sfPersist sfHover')
                .find('> ul').hide().css('visibility','hidden');

            // add children that should be persistent
            if ($(this).is('.sfSelected')) {
                // if previously selected, keep hidden
                menu.find('li.sfSelected').removeClass('sfSelected');
            } else {
                // Hide other selected classes
                menu.find('li.sfSelected').removeClass('sfSelected');
                // if newly selected, then show
                $(this)
                    .addClass('sfSelected') // remember which one is selected
                    .parent()
                    .show().css('visibility','visible')
                    .parent().addClass('sfHover sfPersist');
            }
        });
});

Superfish - On click in the submenu remain open

jQuery