<pre>
<script type="text/javascript">
function addLink() {
    var body_element = document.getElementsByTagName('body')[0];
    var selection;
    selection = window.getSelection();
    var pagelink = " Read more at: <a href='"+document.location.href+"'>"+document.location.href+"</a>"; // change this if you want
    var copytext = selection + pagelink;
    var newdiv = document.createElement('div');
    newdiv.style.position='absolute';
    newdiv.style.left='-99999px';
    body_element.appendChild(newdiv);
    newdiv.innerHTML = copytext;
    selection.selectAllChildren(newdiv);
    window.setTimeout(function() {
        body_element.removeChild(newdiv);
    },0);
}
document.oncopy = addLink;
</script>
</pre>