[sebbe]

PHP Code:

$dbh=mysql_connect ("localhost", "username", "password") or die(mysql_error());
mysql_select_db ("forum_database");

$query = "SELECT username FROM user WHERE usergroupid = 'XX' ORDER BY username ASC";
$result = mysql_query($query) or die(mysql_error());

while(list($username) = mysql_fetch_array($result))
{
    echo $username . "<br />";
}
mysql_close(); 


Just replace XX in the query with your desired usergroupid!