// Uso:
//      <input type="button" value="..." onclick="mudaURL(idSeletor);" />

function mudaURL(idSeletor) {
    
    var seletor = document.getElementById(idSeletor);
    var url = seletor.options[seletor.selectedIndex].value;
    if (url != "")
        window.location.href = url;
}