The presentation was given at the Delos Summer School (Tirrenia, June 2008). This presentation provides an overview of digital repositories, looking at different repository types and dividing them by content type, coverage, functionality and target user group. It concludes with two group exercises, one writing a use case for a web archiving project and the other a business case for sustained funding for an Institutional Repository beyond its start-up phase, to help apply knowledge to real-world situations.