This site is being built as a source of Open Educational Resources to support my textbook on TCP/IP network technologies. I am also exploring a new approach to bulding remixable OER materials. You can see the course code for the book in my GitHub repository. Feel free to submit a pull request if you find something that needs fixing. Thanks in advance.
There is a cool textbook with sketchnote images by Mauro Toselli. Electronic copies are free with a CC-BY license and the print copy is CC-BY-NC.
Each chapter has end-of-chapter questions. Those questions are available as quizzes that can be taken online.