<form action="" method="post" name="myform">
<select name="cars" onchange='myform.submit()'>
  <option value=""></option>
  <option value="volvo">Volvo</option>
  <option value="saab">Saab</option>
  <option value="fiat">Fiat</option>
  <option value="audi">Audi</option>
</select>
</form>
[download]