First of all got this for xmas and its a fantastic game, superb atmosphere and clever design. So i got thinking about possible expansions and came up with the following:
1) Miskatonic University - strange happenings in the halls of MU.
2) Mountains of Madness - a whole campaign exploring the mysterious city of the shoggoths.
3) Dreamlands - unlimited possibilities here.
4) Dunwich - easily done, create some tiles with ramshackle houses and barns then throw in some ancient evil.
5) Some sort of egyptian themed exoansion, maybe based on the story under the pyramids.
There is masses of potential for expansions for this game so will be interesting as to how it developes in the coming years.