Código HTML:
<form name="form1" action="variables.php" method="post">
<input type="text" name="var1" />
<select name="opcion" size="3">
<option value="hola">1</option>
<option value="mundo">2</option>
</select>
<input type="submit" name="submit" value="Enviar" />
recogerias el value de option con $_POST['opcion']