<div id="zeus" class="banner">some content</div>
<div id="zeuss" class="banner">some other content</div>

#zeus {    
    background: green;    
}
#zeuss {    
    background: red;
    display: none;    
}
.banner {
    width: 300px;
    height: 100px;
}

$(document).ready(function() {

    var delay = 3000, fade = 1000; // tweak-able
    var banners = $('.banner');
    var len = banners.length;
    var i = 0;

    setTimeout(cycle, delay); // <-- start

    function cycle() {
        $(banners[i%len]).fadeOut(fade, function() {
            $(banners[++i%len]).fadeIn(fade, function() { // mod ftw
                setTimeout(cycle, delay);
            });
        });
    }

});