Apparently these are old jokes, but my roommate just introduced me to them.
There were a lot of hits when I googled it and many different versions of the same jokes. I synthesized some of them for you to read.
Capitalism: You have two cows. You sell one cow, buy a bull, and get a herd.
Communism: You have two cows. The government takes them and provides you with milk.
Fascism: You have two cows. The government seizes both and sells you the milk.
Socialism: You have two cows. The government takes one and give it to your neighbor.
They are awesome because they are funny, concise, and still able to explain key aspects to each politcal philsophy very simply.