A prime example of Communism in the story comes with the building of the windmill. Communist regimes have traditionally been very big on large-scale projects, which they see as being public projections of the supposed achievements of the governing ideology. A large-scale engineering project, such as a canal, for example, can be used by Communist regimes for propaganda purposes: to show the rest of the world that Communism can be just as efficient and forward-thinking as its capitalist counterparts.
This is precisely the attitude behind Snowball's enthusiasm for the construction of the windmill in Animal Farm. Once completed, the windmill will stand as a proud symbol of the animals' self-reliance—a sign that they can make a go of running the farm on their own without outside help from humans.
Another example of Communism in Animal Farm also comes from Snowball. Not long after the animals have driven Mr. Jones from the farm, Snowball sets about burning the ribbons previously worn by the horses. As well as being symbols of human oppression, the ribbons also separated the horses from the other animals. Under Communism, everyone is supposed to be equal. And so, by destroying the horses' ribbons, Snowball is attempting to usher in a period of absolute equality among all the animals on the farm.