Making life easier.

There are five different types of stone each having its own use:

Bridge stone Places a bridge over a square of water
Boat stone Summons a boat (can only be used next to water)
Dragon stone Summons a dragon (can only be used on flat land)
Gate stone Teleports between gates
Flip stone Teleports to a gate

There are eight gates placed around Uska Bau, they let you teleport between them if you have a gate stone.

These are the locations of the gates:

1. 236-63 - On the penninsular, south-west of Oxbridge
2. 109-153 - Just west of Doggonia
3. 344-160 - On an island, north-west of the Fount of Heaven
4. 139-209 - On the northern tip of the snowbank, just east of Sparta
5. 108-25 - On an island just east of Protection
6. 272-127 - Between Celestial city and the Theatre
7. 01-106 - In the desert area just south of Speed
8. 74-69 - Just north of the road between Cathedral and Kaos

Standing in one of eight positions in the stone circle teleports you to one of the others around the world.
Use this picture with the corresponding circle above so you don't end up stranded on a desert island.

Thanks to TerraBreaks for the information that teleporting isn't random as I believed it was.