[danik.js]

<table id="mytable">
    <tr>
        <td><input /></td>
        <td><select><option>Бла бла</option></select>
    </tr>
</table>
<button id="mybutton">Еще</button>
<script>
(function(){
    var table = document.getElementById('mytable'),
         tbody = table.tBodies[0];
         button = document.getElementById('mybutton'),
         sample = table.rows[0];
    
    button.onclick = function() {
        tbody.appendChild(sample.cloneNode(true));
    }
})()
</script>