"Trends"
I agree with Wombat on this one. I've used:
1. Barony of Giltram
Centralisation of feudal authority, destruction of traditional economies, rebels inspired by the EZLN crossed with Robin Hood.
2. Green Isles
Spanish colonisation of Caribbean, rise of merchant capital, destruction of feudal allegiances, devastation of indigenous communities, primitive capital accumulation.
3. Goblin City of Kreyak
Rise of totalitarian states inspired by Nazi Germany, the British National Party, and the recent media effort for the war in Iraq; the repression of the urban poor, the sacrifice of lives for economic success; the discovery of superweapons like the atomic bomb, the tank, or biological weapons... This was a really dark campaign. It's probably for the best that it didn't last long. The players worked as slave drivers, participated in a fascist coup, and nearly launched a war that would have ended with the deaths of two thirds of the city's population.
Note the party were very much the bad guys here. At one stage they were driving a convoy of slaves to work in the mines, and they spotted one straining against his burden, pushing with all his might but unable to move it. They... (five minutes later) ...as his guts dripped down the ogre's lips and the priest finished his sermon on commitment to one's labours. After the game, one of the players (the priest, actually) reflected, with some discomfort, that the poor little slave had actually been a strongly Christlike image. He's not Christian, but was raised as such and wasn't so comfortable with his role.
It's difficult to "avoid politics" in these matters, as I tend to design my adventures in a way that makes pretty explicit political statements. That doesn't mean I make all of the issues black and white. I try to make all the sides rather despicable, and just put the party in a situation where they're compelled to get their hands dirty somehow (which is itself a political viewpoint). Though I still have my moments of undisguised propaganda, I must admit.