Again, I don't have much MP experience to draw on but LlamaServer seems pretty solid and simple (
http://www.llamaserver.net/). The instructional page is here (
http://forum.shrapnelgames.com/showthread.php?t=35160).
I'm fine with a 24 hour hosting time (with auto-host if all turns are submitted early) for the early game, though that might need to be expanded to 36 hours later on when turns take more than 10 minutes to complete.