$.fn.extend({

    animateCss: function (animationName) {

        var animationEnd = 'webkitAnimationEnd mozAnimationEnd MSAnimationEnd oanimationend animationend';

        $(this).addClass('animated ' + animationName).one(animationEnd, function() {

            $(this).removeClass('animated ' + animationName);

        });

    }

});

​

$('article').each(function(index) {

    $(this).delay(500*index).queue(function() {

         $(this).animateCss('fadeInUp');

     });

});