Bookdown
Bookdown is an open source R package that structures book writing and workflow. Those who want to create statistics and programming textbooks may find it a useful fit.
GitBook
GitBook is an online platform to create and host books. It can output your content as a website or as an ebook (PDF, ePub or Mobi). Hosting is free if the book is open. GitHub users will likely feel most comfortable with GitBooks.
Ketty
Ketty is an open source platform for building and customizing streamlined, scalable professional book production workflows using rich web-based tools. The Open Education Network is currently piloting Ketty. Contact open@umn.edu for more information.
LaTeX
LaTeX is a typesetting system designed for making technical and scientific documents, and is available as free software. Authors who write textbooks that include formulas frequently select LaTeX.
LibreTexts
LibreTexts is an open education resource platform for creating, customizing, and sharing accessible, interactive textbooks, adaptive homework, and ancillary materials.
Manifold
Manifold works with the files you've created (Microsoft Word, Google Docs, HTML and others) and converts that existing content into responsive online texts that can be annotated and augmented with rich media. The Open Education Network is currently piloting an instance of Manifold.
Pressbooks
Pressbooks is a publishing platform educators used to create, adapt, and share accessible, interactive, web-first books. It's built on WordPress, so anyone familiar with using WordPress and a WYSIWYG may be comfortable using this tool.
Pressbooks offers a discount to OEN member institutions. STLCC is an OEN member.
Publishing platforms and tools that are frequently leveraged for open textbook production are highlighted above. For a more comprehensive look, see these in-depth overviews: