The Open Science grid consists of computing and storage elements at over 100 individual sites spanning the United States. These sites are primarily at universities and national labs and range in size from a few hundred to tens of thousands of CPU cores. The distributed nature of these resource providers allows users from a single VO to submit their jobs at a single entry point and have them execute at whatever resource is most available. Sharing is a core principle of the OSG. Over 100 million CPU hours delivered on the OSG in the past year were utilized opportunistically, i.e., wherever there were resources available that would otherwise have remained idle. This aspect of the OSG is what allows individual researchers who might not otherwise have access to large computing resources to do so. If you represent a university computing cluster and are interested in providing computing cycles opportunistically to the OSG, contact us at [email protected].