Skies of Arcadia allows you to connect to their website and download additions for the game. These are then deleted from the card and added to a save game. Each of the three packages takes four blocks of space on your card.
One of the three packages that you can download gives you an extra boss to fight. The boss is none other than a Giant Looper that takes on your ship! Like all Loopers it is easily spooked and will run when provoked, never to return! After you have found the Looper's Nest head due north to find this evil monstrosity. Killing this thing just makes you feel so good, as if you were getting giant payback for the annoyances that are its little cousins! Plus, the Captain's Stripe you get for beating it does help too! Beating it is simple. Use Urala to max out your ship's SP on the first round and then guard for the rest of the first round. At the end of the second round, send out torpedos. These must land on the same round that you can use the Moon Stone Cannon on. On the third round, use the Moon Stone Cannon, and it, as well as whatever torpedoes hit, should deal enough damage to kill the beast! By putting all the damage into a single round, you can kill it without scaring it off! Yay!
Another of the downloads adds an extra island to the map. This island is called Hamachou Island and it is above both the Dark Rift and the clouds. Go here to get an extra Cham, and to find out your combat, fishing and treasure-hunting stats. Other than that, there is little use for this place!
The third download unlocks a pair of secret weapons for Aika and Vyse. You can buy them from the Mystery Merchant at any point in the game, as long as you can afford the prices. The Mystery Merchant randomly shows up in the various inns in the game, so look out for him! I won't reveal anything about them!