This document summarizes a presentation given to librarians about how libraries can partner with used book sellers like Alibris and Better World Books to supplement their collections. The presentation discusses how libraries can sell used books through these marketplaces and use the platforms to acquire out-of-print and hard-to-find titles to fill gaps in their collections. It also highlights the services and tools these companies provide for libraries, such as consolidated shipping and collection development reports. The presentation envisions future enhancements like expanded music/movie offerings and regional outreach programs to help libraries build well-rounded collections.