var marquee = $('div.marquee');
marquee.each(function() {
    var mar = $(this),indent = mar.width();
    mar.marquee = function() {
        indent--;
        mar.css('text-indent',indent);
        if (indent < -1 * mar.children('div.marquee-text').width()) {
            indent = mar.width();
        }
    };
    mar.data('interval',setInterval(mar.marquee,1000/60));
});​

<div id="scrollcontainer" style="postion:relative; overflow:hidden; width:100%;">
  <span id="scrolltext" style="position:absolute; white-space:nowrap">this is the scrolling text</span>
</div>

function scroll() {
  $('#scrolltext').css('left', $('#scrollcontainer').width());
  $('#scrolltext').animate({
    left: '-='+($('#scrollcontainer').width()+$('#scrolltext').width())
  }, 2000, function() {
    scroll();
  });
}

scroll();