It's far from complete, but http://www.truered.net/mfw/MainPage True Red's page has some basic info on past GMs and important events and people in the MFworld.

http://www.truered.net/mfw/MFWorldPlaces will get you more specifically to the place where you can see the established locations of the Mobius Forum World. There is no map of the city or the world proper, but under the "Sega City" entry it mentions the general nature of Sega City as far as geography near it goes, including that it's actually a dockside city, and there is Mt. Kitsune somewhere around it outside its borders.

Of course, if ever writing your own MoFiction, it's a flexible enough setting that you can pretty much assume that if anything needs to exist for the sake of the story, it will exist for the sake of the story. Narrativium at work. =P