While the Wikimedia Foundation is best known for its flagship project, Wikipedia, and the MediaWiki software that powers it, the Foundation's open-source ecosystem extends far beyond these well-known projects. In this talk, we will explore the fascinating world of Wikimedia's open-source tools ecosystem and the cloud infrastructure that makes it possible. We will showcase some of the coolest tools and projects, and we will highlight the unique opportunity that the Foundation offers for contributing to its cloud infrastructure – a rare chance to work on infrastructure for a cause that does good in the world, supporting the Foundation's mission of providing free and open knowledge to the global community. Whether you are a seasoned open-source developer or a newcomer to the field, this talk will provide valuable insights and inspiration for getting involved in Wikimedia's vibrant community of contributors.