Get the visible elements in a jquery.jcarousel

demo code below...

Setup Carousel

 $(document).ready(function () {

            $('#featured_carousel_list').jcarousel({ 
visible: 4, 
scroll: 4, 
initCallback: mycarousel_initCallback, 
buttonNextHTML: null, 
buttonPrevHTML: null,
itemFirstInCallback: function (carousel, liElement, intemIndex, action) {
                    // get URL's of visible items
                    var item_URL = $(liElement).children('a:last-child').attr('href');
                    alert(item_URL);
                }

            });


        });

        function mycarousel_initCallback(carousel) {
            $('#next_button').bind('click', function () { carousel.next(); return false;});
            $('#prev_button').bind('click', function () { carousel.prev(); return false;});
        }

HTML List

<div id="prev_button"><<</div>
<div id="next_button">>></div>
    <ul class="featured_carousel_list" id="featured_carousel_list">
        <li><img src="images/item_sample_image.gif" alt="" width="180" height="90" /><a href="display.aspx?tid=1" class="item_text_link">title</a></li>
        <li><img src="images/item_sample_image.gif" alt="" width="180" height="90" /><a href="display.aspx?tid=2" class="item_text_link">title</a></li>
        <li><img src="images/item_sample_image.gif" alt="" width="180" height="90" /><a href="display.aspx?tid=3" class="item_text_link">title</a></li>
        <li><img src="images/item_sample_image.gif" alt="" width="180" height="90" /><a href="display.aspx?tid=4" class="item_text_link">title</a></li>
        <li><img src="images/item_sample_image.gif" alt="" width="180" height="90" /><a href="display.aspx?tid=5" class="item_text_link">title</a></li>
        <li><img src="images/item_sample_image.gif" alt="" width="180" height="90" /><a href="display.aspx?tid=6" class="item_text_link">title</a></li>
        <li><img src="images/item_sample_image.gif" alt="" width="180" height="90" /><a href="display.aspx?tid=7" class="item_text_link">title</a></li>
        <li><img src="images/item_sample_image.gif" alt="" width="180" height="90" /><a href="display.aspx?tid=8" class="item_text_link">title</a></li>
    </ul>

If I understand your question correctly then you want to get the URLs of all the visible elements. You can achieve this by replacing your itemFirstInCallback callback with a itemVisibleInCallback:

itemVisibleInCallback: function(carousel, liElement) {
  var item_URL = $(liElement).children('a:last-child').attr('href');
  console.log(item_URL);
}

This callback will be triggered for all 4 items as they turn visible.