var nextNum = 0;

function slideSwitch() {
    var $active = $('#slideshow img.active');

    if ( $active.length == 0 ) $active = $('#slideshow img:last');

	var $sibs  = $active.siblings();
	nextNum = (nextNum+1) % $sibs.length;
	var $next  = $( $sibs[ nextNum ] );

    $active.addClass('last-active');

    $next.css({opacity: 0.0})
        .addClass('active')
        .animate({opacity: 1.0}, 1000, function() {
            $active.removeClass('active last-active');
        });

}

$(document).ready(function(){
       setInterval( "slideSwitch()", 5000 );
});