Snowpiercer, a science fiction movie playing in limited release in the US is one of the best movies about class stratification I've ever seen.
A short (no spoilers) synopsis:
In the near future, humanity finally responds to global warming with some sort of cold bomb which results in the entire earth being frozen over. No life remains, except for passengers on a self-sustaining train that circles the earth.
The train is divided by first, second, and third class passengers - all depended on which tickets were bought before the big freeze. The third class passengers live in squalor in the back, the first class live in luxury at the front, and the second class passengers act as servants and police. 17 years after the big freeze, the 3rd class plots a revolt.