in the WA_Globals file, change the subject:
$WAGLOBAL_Contact_Email_Subject = "Online Contact Form Response" ;
to:
$WAGLOBAL_Contact_Email_Subject = "Online Contact Form Response ".isset($_POST['selectListName'])?$_POST['selectListName']:""."" ;
where selectListName is the name of the select list.
the same strategy can be used for the to address, but the value of the select list would nee to pass an email address.