According to its creator Peter Suber, "Nomic is a game in which changing the rules is a move. In that respect it differs from almost every other game. The primary activity of Nomic is proposing changes in the rules, debating the wisdom of changing them in that way, voting on the changes, deciding what can and cannot be done afterwards, and doing it."
So what I propose is a game of this sort on the Webdiplomacy forum. I've already set up some preliminary rules. All you have to do is post your interest in this thread and you immediately become a player! From there, you can propose, discuss, and vote on changes to the rules.
A link to the rules and rule changes: http://tinyurl.com/WebDipNomic
I am Gamemaster, meaning that I do all of the tabulating of the votes and the changing of the rules. I also resolve any disputes and ambiguities, so post here if you don't understand anything. If you can't access the rules, please post here and I'll transfer them somewhere else.
Have fun!