... Toulan, Ancient Greece, Next Island... Not sure if they have forums for those or not, someone can provide a link if they do.
Ancient Greece is part (a submap) of Next Island. No fee any more to enter Greece - ignore the outdated mission dialogs and just use the teleporter in the cave (ask in Rookie or #nextisland chats for its location and other info). I think both Next Island and Toulan have forums, but I don't have links for them. BIG Industries family of societies is a great source of information about Next Island / Ancient Greece - for example Blastoise Meculus or Danny Ped Super. Simone Wauspaus Kelleners has also been very helpful in-game with information lately.
Text directions to get into Greece: Cross the river West of Orpheus TP, follow the trail that has minotaur parts next to it, there's a cave by a pond above a waterfall, the trail leads to the cave. The TP that's inside that cave goes nowhere but Ancient Greece. It's a lot simpler with a waypoint (right clicking the map creates a waypoint now which is pastable and clickable in chat).
If you are a miner by profession, you may want to go mining in Hell, Monria and Arkadia Underground, which I believe are all 'indoor' mining locations.
Indoor mining has different, more challenging mechanics than outdoor mining. Bring skills and a nice finder.
Indoor mining that I know of otoh: FOMA, Monria, Arkadia Underground, Rocktropia's Hell. These are implemented as submaps of a planet, which implies that THING and Greece should also work like indoor mining; but I've mined Greece a lot, and can verify that it acts just like outdoor rules there. Additionally, the only ore I've ever found on Greece or THING is Lyst, and the only enmatter Crude.
Ancient Greece is a submap of Next Island.
Hell, THING (aka Headjack or Arctic), and Secret Island are submaps of Rocktropia.
Hub (a PvP arena) is a submap of Cyrene.
Arkadia Underground is a submap of Arkadia.
Thule, the usual tutorial, is a tiny submap of Calypso.
FOMA, CP, and Monria act like submaps of something, and details about behaviour of certain missions on Monria indicate that it is mechanically part of Calypso.
I don't know of any Toulanb submaps.
On a nearly unrelated note, every mothership sits on two tiny maps (Hangar on one, the rest of the ship on the other) which only intercommunicate via teleporters. This is not the case with privateers, which don't have hangars.
Cheers