friend_lists.php

$me = PUT_YOUR_UID_HERE;

$friends = user_get_reciprocal_friends($me);
$friends_info = user_multiget_basic_info($friends);

$male_friends = array();
$female_friends = array();
foreach ($friends_info as $uid => $friend_info) {
if (gender_is_male($friend_info['gender'])) {
$male_friends[] = $uid;
}
if (gender_is_female($friend_info['gender'])) {
$female_friends[] = $uid;
}
}
friend_list_create($me, 'Dudes', $male_friends);
friend_list_create($me, 'Girls', $female_friends);