Script

(function($){
    $.fn.tabPanel = function(){
        var tabArea = $(this); // this == $(object)
        var tabPanel = $('div.tabPanel',tabArea);
        var tab = $('ul.tab li',tabArea);
        
        var tabSet = function(target){
            var targetTabId = $('a',target).attr('hash');
            
            tab.removeClass('active');
            tabPanel.hide();
            $(target).addClass('active');
            $(targetTabId).show();
        }
        
        tab.click(function(){
            tabSet(this);
            return false;
        }).each(function(){
            if($(this).hasClass('active')){
                tabSet(this);
            }
        });
        
        if(tabPanel.filter(':visible').length!=1){
            tab.eq(0).addClass('active');
            tabPanel.not(':first').hide();
        }
    }
})(jQuery);

// 実行する
jQuery(function($){
    $('div.tabArea').tabPanel();
});

Demo