This website provides information about making material you've created available using a Creative Commons license, which can allow others to freely and openly use or remix your work, depending on which type of license you choose.
This website, created by an instructor at Western Washington University, is an online platform that helps professors create online interactive texts. Note that texts created through this tool are inexpensive but not free of cost for students.
This site, created and maintained by the Johns Hopkins School for Public Health, provides access to open courseware and course materials for various health-related courses. Note that the textbooks assigned, however, are not always open textbooks.
This website, created by the Massachusetts Institute of Technology (MIT), provides access to open course materials from a wide variety of classes. These materials can include video lectures, online textbooks, exams, assignments, problem solving videos, lecture slides, and more. Note that not all textbooks assigned are open textbooks.
This website, hosted by Washington state community and technical colleges, offers a gateway to open course materials for various introductory courses. Note that the materials themselves are hosted in Google Drive; login is not required for access. Not all textbooks assigned by these courses are open.
This website, created by students and faculty at UC Davis, is a set of interconnected pages put together to replace traditional textbooks. This type of site could be used as a model if you wanted to create your own class website or wiki in place of a textbook.