<form>

  <select name="adi">
	<option value="mehmet" class="mehmet">Mehmet</option>
	<option value="kilimci" class="kilimci">Kilimci</option>
	<option value="ahmet" class="ahmet">Ahmet</option>
 
  </select>  
  <select name="adi">
	<option value="mehmet" class="mehmet">Mehmet</option>
	<option value="kilimci" class="kilimci">Kilimci</option>
	<option value="ahmet" class="ahmet">Ahmet</option>
  </select>  

</form>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"></script>
<script type="text/javascript">
$('select').change(function() {

    var value = $(this).val();

    $(this).siblings('select').children('option').each(function() {
        if ( $(this).val() === value ) {
            $(this).attr('disabled', true).siblings().removeAttr('disabled');   
        }
    });

});

</script>