Inspired by The Last Express, a beautiful and elegant videogame set in 1914 which I did a Game Translation on, I've been running a play-by-post game using the Call of Cthulhu system and setting over here. You can see the written trailer over here which has a nice set of pictures and introductory statements that I think helps advertise it.
The game is built on a different premise to most play-by-posts that makes it more robust to player attrition, which is good, because so far I have lost about 10 players. Basically each player develops a character independently of the others and boards the train with their own goals to complete. These goals might be mundane and sociable or they might be intensely malevolent or even supernatural.
Generally most of the goals have been inadvertently at cross purposes though there's been thus far a distinct lack of lizardmen and a greater number of academics than I thought would happen. So much for opening the floodgates by making that a possibility!
Basically each individual then boards the train which contains both NPCs and PCs where they are slowly exposed to stranger and stranger details until finally they're hooked into one adventure or another. Since they're not encouraged to investigate together (though that does occasionally happen), there's less likely to be bottlenecks where one player drops out and the game grinds to a halt as the other players are forced to wait -- often dropping out themselves as they grow bored of waiting.
The main threat to this game's sustainability is that only self-motivating players can get involved. Those who are easily confused or too timid to take an excuse to involve themselves or talk to people quickly find themselves lost and alone. I've tried to help that where I can but it's still pretty hard in this sort of game.
On the plus side, no other traditional play-by-post would survive the kind of player attrition I've had. The game also moves quite quickly (generally 15 minutes passes each week or whatever time interval would take them to the next stop with Time Stamps placed to remind them) which it couldn't do if we all had to wait for the same folks to post.
Especially since there's about 5 - 8 active players at this time (at different rates of activity).
So the first day is done and now the night time antics are beginning, if any of my beloved readers would like to dip their toes in, now is the time! Mosey on over here to sign up and get involved!