In this report we provide an overview of digital reputation management systems for virtual communities. We begin with a discussion on the how trust is created in the real world. We then highlight how the process of trust creation differs in the virtual world. Next, we talk about the different ways in which digital reputations are useful to virtual communities such as incentivizing cooperation and punishing malicious users, providing recommendations or as a form of distributed authentication. We then discuss how evolutionary biology and game theory have informed research in reputation systems. This is followed by a discussion of the various components of reputation such as context, the forms of evidence, first and second order reputation and architectural considerations including the role of distributed hash tables in decentralized reputation management systems. We conclude with a discussion of some reputation management systems such as complaints-based trust, EigenTrust, PeerTrust and ROCQ.