LeMill is a collaborative digital learning resource authoring tool that allows teachers to remix, adapt, and share educational content. It is based on open-source software and has over 7,000 users. Within LeMill, teachers can collaboratively author web pages, exercises, lesson plans, and other content types using templates. Content can be organized into collections and shared within communities of educators. All resources created in LeMill are released under Creative Commons licenses to enable further adaptation and reuse.