There's a new MMO on the block going by the name Cthulhu Returns. Apparently, it's wall-to-wall Lovecraft -- the game boasts that you'll find every location mentioned in the Lovecraft canon somewhere in the game -- and completely free.
It's not the first Cthulhu MMO, what with CthulhuMud and Cthulhu Nation having been around for some time, but it seems to hit all the right notes, despite the cutesy J-RPG graphics:
Cultists are not for the faint of heart, and have some notable differences from regular professions. They can be attacked by anyone, are treated as criminals by police, and are ignored by some shopkeepers. Keep searching, or ask a Cultist player...if they aren't busy trying to kill you. The Cultist profession master is hidden, and cultists can be very secretive.
More information here, and you can download the open beta here.