Digging around, I found this kingdoms module I wrote way back in the ancient times of a few years ago. It's incomplete, but pretty full-featured. I'd be happy to get with anyone and fix any bugs, problems or try to support it if I can. I will remind folks that this is unfinished and had to be modified quite a bit to get it to work with a stock system. It compiles cleanly on SmaugFUSS 1.8 under g++ 4.1.2. All you need to do is add the following to the pc_data struct in mud.h:

struct kingdom_data *kingdom;
char *kingdom_name;

There's function calls you need to add to db.c and other such places to integrate the module into the MUD, but you should be able to get a basic idea of how it works without doing so.
Let me know what you guys think.