Western Fairy Island
Fishman: He tells you that you can steal items using the Rito Grappling Hook, and that Bokoblins carry Joy Pendants.
Great Fairy: More arrows.
The entrance to the Great Fairy Fountain on this island is blocked, but can be opened by using the Skull Hammer on the nearby switch. She will upgrade Link's quiver capacity to 60 or 99 arrows.
Rock Spire Isle
Fishman: All that lighthouse on Windfall Island needs is a good spark, and it will be able to shine again.
Contents: Heart Piece, Bottle, Treasure Chart 4, Treasure Chart 37.
The Heart Piece, Bottle, and Treasure Chart 4 are available from the (rather odd) Beedle here, for 950, 500, and 900 rupees respectively.
Treasure Chart 37 is in the cave on the island, guarded by a flock of Keese. Destroy the boulders to reach the summit, then enter and slay them to earn the chart.
Tingle Island
This island is ravaged by Cyclos, and acts as a warp destination.
Fishman: He reveals that Tingle is a 733t map-decyphering dude, but that he charges quite a fee for his services.
Big Octo: Heart Piece.
This island is home to Tingle, who will decypher any Triforce Charts that you might have. He charges 398 rupees for each one, though, so a large wallet is a requirement.
Northern Triangle Island
Treasure: Octo Chart, found using Treasure Chart 26 from Six-Eye Reef.
The Octo Chart shows all of the Big Octos, with a label denoting the number of eyes they have. The southernmost Big Octo is marked in red, as it is a special one.
This tiny island is home to one of the Great God idols. Insert the Pearls in this and the other two to open the path to the Gods.
Eastern Fairy Island
Great Fairy: More bombs.
After destroying the stone obstructing the entrance to the Great Fairy Fountain, she will upgrade Link's bag to carry 60 or 99 bombs.
Fire Mountain
Fishman: A great treasure is rumoured to be contained within the mountain, but it will need to be cooled down before you can get inside.
Contents: Power Bracelets.
This flaming pile of molten lava can be cooled by firing an Ice Arrow into the jet of fire spewing from its peak. This will allow access for just five short minutes, in which you must climb to the top, enter the mountain, and destroy all of the monsters therein to earn the Power Bracelets and boost Link's strength.
Star Belt Archipelago
Fishman: The Ghost Ship appears here on nights when the left half of the moon is missing.
