As the field of digital libraries matures and new systems and standards develop, the ability to interoperate between systems becomes paramount. This tutorial gives a practical introduction to many recent standards and de facto standards for interoperability, and illustrates them using open source digital library software-including online demonstrations of interoperation issues and solutions. Core standards that are discussed include Dublin Core, OAI-PMH, METS, and MODS. We use interoperation between Greenstone and DSpace as a motivating case study. For those demonstrations that involve Greenstone, attendees who wish to may bring their laptops, install Greenstone from a CD-ROM that we will provide, along with various sample files, and follow along with the demonstrations on their own machine.