jQuery slowEach

jQuery.slowEach = function(array, interval, callback) {
    if(!array.length) return;
    var i = 0;
    next();
  
    function next() {
        if(callback.call(array[i], i, array[i]) !== false)
            if(++i < array.length)
                setTimeout(next, interval);
    }
      
    return array;
};
  
jQuery.fn.slowEach = function(interval, callback) {
    return jQuery.slowEach(this, interval, callback);
};

// sample usage  
$(document).ready(function() {
    $('.reveal').slowEach(500, function() {
        $(this).show();
    });
});