The objects of study of this paper are swarming systems, a special kind of peer-to-peer systems where users interested in the same content at the same time cooperate with each other. In particular, we consider the problem of how to combine files into bundles in such systems. First, we analyze the case of a monopoly where a single publisher decides how to aggregate its files so as to satisfy user demands while mitigating its serving costs. We establish conditions for the existence and uniqueness of an equilibrium and how the publisher's bundling strategy affects its profit. Then, we consider the competitive case where bundling decisions of one publisher affect the outcome of other publishers. Using normal form games we analyze the impact of different system parameters on the Nash equilibrium.