1. There is one along the path of the chain of rocks on the right side of the NW map (follow it and you'll find it ;),
2. the second one is on the SW map. go south to the very bottom left side of the long chain of rocks. you'll see that there are 3 rocks at the bottom forming a triangle, go there.
3. the third one i found is in the NW map if you go up to the very top, on the left side of Bannan island, you will find Zaus island. hope that helps a little :).
4. A fourth one is called Dee Ess Island, it is to the right of goron island past goron islands rock trail in the SE map. It looks like a DS.
5. the last one i found (and i think that's all there is) is called "maze island" which can be found at the very top of NE map, in the big empty space near some small rocks (float around, you'll see it. i found it wihle being attacked by pirates).
i think that's all but u can find islands by going into large empty areas in the sea that seem far from the others and a place u normally wouldn't go to :)
There are many uncharted islands, at least one per map.
it is one of the uncharted island in the 2nd sea chart
you have to get the northeastern seachart that's how to go to that place
That would be the Isle of Ruins.It's in the Northeastern sea at the top left corner.
Yes,you can find items on mercay island for phantom hourglass,in the temple of the ocean king.You can find the the southwestern sea chart (no requirements),the phantom hourglass,the northwestern sea chart (after you beat the temple of fire for both),the southeastern sea chart and the northeastern sea chart (after you beat the ghost ship for both).
you go to the northeaster sea. Goron island is your first stop when you get there.
it is a mode unlocked on freedles island where with another player of phantom hourglass can trade items with you
Molaida Island
you get the hammer in pyramid island
On the island of ruins
yftyffgfdcrdrx
Cannon island