This National STEM Digital Library (NSDL) project develops a service that gives educators and students the ability to create personal collections of resources from the NSDL and other digital libraries. To use the current (approximately 230,000) digital resources in the NSDL effectively, educators and students need to retain them, share them and return to them, just as they do with printed materials. This project addresses this need by providing the equivalent of a personal digital library, allowing patrons to store digital library holdings together with the associated identifying metadata. In addition, the Personal Collection service enables users to classify resources using personal taxonomies or organizational schemes, add annotations (such as the suggested citation), share collections with colleagues in collaborative learning and research settings, and search colleagues personal collections using metadata. Users can also create "packages" of resources and learning objects for use by learning content authoring tools and learning management systems. The service has two parts, a Personal Collection server, based on Dspace, and a cross-platform client called Keeper that runs in a user's Internet browser. The design is based on Internet services architecture and makes maximal use of existing open source technologies. This project holds the promise of making NSDL collections more practical to use, and therefore more accessible to educators and students alike.