Peer-to-peer sharing systems are becoming increasingly popular and an exciting new class of innovative, internet-based data management systems. In these systems, users contribute their own resources (processing units and storage devices) and content (i.e., documents) to the P2P community. We focus on the management of content and resources in such systems. Our goal is to harness all available resources in the P2P network so that the users can access all available content efficiently. Efficiency is taken both from (i) the point of view of the system, in that we strive to ensure fair load distribution among all peer nodes, and (ii) from the point of view of the users, in that we strive to ensure low user-request response times. We propose a novel architecture for this new class of applications, which differs drastically from what is either found currently in existing products or proposed in academia. We contribute and study novel solutions that achieve our goals, while at the same time addressing the formidable challenges due to the autonomy of peers, their heterogeneous processing and storage capacities, their different content contributions, the huge system scale, and the highly dynamic system environment.