Cultures & Demeanors Mod. It's not really a full-blown mod per se, it's more of an add-on to add some flavour and make your Culture selection actually matter (immensely) with regard to your style of play. I'm working on a new version, I'll see if I can put it up here someday soon.
It's really nice to see the C&D Mod mentioned once in a while, you know
