This paper presents iShare, a distributed peer-to-peer Internet-sharing system, that facilitates the sharing of diverse resources located in different administrative domains over the Internet. iShare addresses the challenges of resource management in desktop grids, and integrates these resources with production grids. In this paper, we present a brief overview of the iShare system and describe how iShare leverages existing standards to provide novel solutions to the problems of resource dissemination, resource allocation and trust in desktop grids. We also discuss how iShare integrates production grid systems, such as the Teragrid, with desktop resources and compare the iShare approach with web-based user portals for production grids. To quantitatively evaluate our techniques, we measured the efficiency of resource allocation in iShare and the overheads associated with establishing trust and providing the iShare user interface for production grids. The evaluation results demonstrate ...