Information seekers are generally on their own to discover and use a research library's growing array of digital collections, and coordination of these collections' development and maintenance is often not optimal. The frequent lack of a conscious design for how collections fit together is of equal concern because it means that research libraries are not making the most of the substantial investments they are making in digital initiatives. This paper proposes a framework for a research library's digital collections that offers integrated discovery and a set of best practices to underpin collection building, federated access, and sustainability. The framework's purpose is to give information seekers a powerful and easy way to search across existing and future collections and to retrieve integrated sets of results. The paper and its recommendations are based upon research undertaken by the author and a team of librarians and technologists at Cornell University Library. The team conducted structured interviews of forty-five library staff members involved in digital collection building at Cornell, studied an inventory of the library's more than fifty digital collections, and evaluated seven existing OAI and federated search production or prototype systems. Discusses the author's team's research and the rationale for their recommendations to: present a cohesive view of the library's digital collections for both browsing and searching at the object level; take a programmatic (rather than project-based) approach to digital collection building; require that all new digital collections conform to library-developed and agreed-upon OAI best practices for data providers; and implement organizational structures to sustain the library's digital collections over the long term.