nationstates.net general forum has an international politics forum which is more active than Atlas and is significantly more diverse (in gender, location, race, religion, ideology, etc). There is a significant proportion of nation-states users who are ideological extremists/hacks with whom you can't have an intelligent discussion but you could say that about Atlas too. Also the discussion is a lot less cartographical than atlas. The site is based on a nation-state role-playing game. I used to lurk there for a short time. See for yourself:
https://forum.nationstates.net/viewforum.php?f=20
