Well, inspired by Adventuria Online, I've begun work on my own online solo game. It's hosted on my own page, here.
So far it's pretty small - the foreign quarter, park, docks, sewers, and a moderate portion of the amenities work. It's expanding fairly rapidly, though - a few days ago, it was just an idea.
The rules do get revised fairly regularly, for balance, so it's important to recheck them from time to time if you do choose to play.
I'm interested in hearing any comments on it, particularly ones related to game balance.