The number, size, and availability of scientific datasets have grown enormously over the last few years. As scientific activity becomes more data intensive and collaborative, a key challenge for cross-disciplinary research will be discovery of diverse data sets, managed within distributed repositories and registries. Currently, discovery of information on the Internet is largely performed through automated approaches, characterized by web crawling and associated algorithms, or labor intensive indexing and categorization, such as the National Library of Medicine index for medical literature. There are significant amounts of data housed in repositories where only researchers with expertise in the specific field know and access the data.<br/><br/>This project builds a user driven architecture for data discovery (UDADD), a capability that enhances discovery of scientific datasets by building a global index from diverse communities with minimal input. In the UDADD approach user actions, such as dataset queries or downloads, drive the construction of a global index. These actions are recorded and gathered automatically, through cooperation with repository managers. Two software plugins are provided to help the repositories interact with the UDADD system. The architecture includes ranking techniques based on frequency and recency of use of the datasets. <br/><br/>The pilot architecture will be demonstrated and evaluated using cooperating repositories within the DataNet Federation Consortium. Currently, six science and engineering communities participate in the consortium, including national scale projects in oceanography, social science, cognitive science, hydrology, engineering, and plant biology.