Played a few rounds of South Seas with the Friday expansion and must say I wouldn't play the base game without it now! Here are some loosely translated rules for Friday:
(Front page)

Game material
-1 wooden figure Friday
-6 landscape maps with symbols and other backs
Game preparations
All rules of Carcassonne South seas remain in place.
The cards are shuffled and the extension placed face-down separate from the normal landscape cards. The landscape map of Carcassonne South are divided into 10 stacks of seven cards. The stacks are placed in a row. The other two cards are the last (11th) stack.
Gameplay
On the player's turn, the landscape cards must always be drawn from the front stack, so that the stacks are depleted sequentially. When a batch has been used up, then a week is over. Now comes Friday in appearance and discovers his island. He will give all players special bonuses.
The player who is on the line, after a batch has been used up, reveals an expansion card first before he performs his normal turn. On this card face-up, it is Friday. The expansion cards thus expose players to a small island of"Friday". Players should roughly build the map of this island as above.
After the player has discovered a part of the island, he draws a normal landscape cards from the front deck and makes his normal turn.
This continues now after each 7 stack, until the entire island has been discovered by Friday.
When Friday finds all 6 parts of the island, the player who would have made the next discovery, must move Friday to a different part of the island his choice. The island that Friday is placed on, all players can use the bonus.
(Back page)

Example (with photo): The last card from deck 4 was created. The next player puts one of the expansion cards and presents on Friday. The following week (7 cards of 5 stack), each more, 1 clam gets when he gets sea shells.
Special bonuses of the Friday island
-+ 1 Shell + 1 banana + 1 fish
Every time when a player is scoring a feature and receives one or more of the goods, he receives another one of those goods.
-1 less good for deliveries
Each player supplies a vessel with one less good, as the ship usually requires. These goods can freely be chosen by the player.
-Trade in goods
Each player may now before he put on the map in his turn, trade with other players. He can ask his teammates, whether with him goods want to share. The trade is voluntary, the player may decide freely whether they join the trade. Only goods may be exchanged. The player on the train may share with several players. It may be traded only with the active player. A trade between other players is prohibited.
-Islander insert and withdraw
Players must first insert an Islander on the specified map in their drawn tile, and then again withdraw an Islander from the playing field. It must be executed in this order.