Okay, I got my leader registered, so I have seen the diplomacy section. Thanks. I have to say, it looks pretty great. From the features you've talked about implementing, my own brief time as an admin for a Pitboss game and a player for another, and my imagination I've come up with a list of suggestions. I'm not sure how possible they all are, and I have to say that the service was already amazing yesterday with just an RSS feed, but maybe these will spark something for you.
* Group Diplomacy, and Public postings. If the recipients of a diplomatic message were listed as check boxes, instead of a pull down menu, we could send a message to several people at once. Incoming messages could indicate everyone who received a message, so we'd always know who's involved in which diplomacy. A checkbox for "All" would post the message to everyone.
* Is it possible to limit diplomacy to just civs that the player has met? You seem able to extract data from the game, so this may be possible. This is mostly a "house rule" kind of thing that I bring from SMAC PBEM... nobody can discuss the game without contact. It works on the honor system really, but if you implemented it it would allow a message to "ALL" players to filter out those that would, according to the rules, not be able to get it.
* A scheduling service. What I imagine here is that players could see a calendar where they could input times that they could get online to play. When all the players have a block of time that coincides for 30 minutes, an email is sent out alerting everyone of a possible play time, and a message on the game's page appears saying the same. Alerts could also go out when, say, 80% of the players could do a particular time so that the others could check their schedule. This would alleviate the need to handle this business over messaging programs or email, where in my experience it is very inefficient. Massive group emails only work when people are highly organized, and random groups of gamers don't always tend to be.
* Out of Town flag. If a player won't be able to play for a few days, he can tell Civstats, and a message on the main gamestats page would inform everyone of that.
* Hold up notifiers. Sometimes everyone has played excpet for ONE PERSON, maybe 2 in a big game, and there are 18 hours to go.
If I am ever that person I wouldn't mind an email telling me so, since I might be able to squeeze in the turn before work, instead of getting home from work like I usually do. Of course, some would hate the nagging, so if it was an option that'd be better.
Am I right that all communication between Civ and your program is only one way?