var nav     =    document.getElementById('nav'),
    links   =    nav.getElementsByTagName('a'),
    select  =    document.createElement('select'),
    option  =    document.createElement('option');

for (var i = 0; i < links.length; i++){
    var link    =    links[i],
        _option =    option.cloneNode(false);
    _option.value = link.href; // Set the option's value to the original link
    _option.innerHTML = link.innerHTML; // Set the option's text to the original text
    // if this link matches the current URL, add a selected attribute
    if( window.location.href == link.href ) {
        _option.selected = 'selected';
    }
    select.appendChild(_option);
};

select.addEventListener('change', function() {
    window.location = select.value;
}, false);

nav.parentNode.insertBefore(select, nav);
nav.style.display = 'none';