- AIM (Math) – http://aimath.org/textbooks/approved-textbooks/
- Bccampus Open Textbooks – http://open.bccampus.ca/find-open-textbooks/
- Book Bucket – https://archive.org/details/lardbucket2012books?&sort=-downloads&page=2
- bookboon.com – http://bookboon.com/
- Boundless.com – https://www.boundless.com/subjects/
- Center for Computer-Assisted Legal Instruction – http://www.cali.org/the-elangdell-bookstore
- College Open Textbooks – http://www.collegeopentextbooks.org/
- Coursera Textbooks – https://www.coursera.org/courses?query=textbook&languages=en
- DPLA (Public Domain Textbooks) – http://dp.la/search?q=textbook&utf8=%E2%9C%93
- Flat World Education – http://catalog.flatworldknowledge.com/
- FreeTechBooks – http://www.freetechbooks.com/
- Global Text Project – http://globaltext.terry.uga.edu/
- Google Books (Public Domain Textbooks textbooks)
- HippoCampus (video textbooks) – http://www.hippocampus.org/
- InTech (Science) – http://www.intechopen.com/
- Internet Archive (PD) – https://archive.org/details/internetarchivebooks?and[]=textbook
- Lumen Learning – https://courses.candelalearning.com/catalog/lumen
- MERLOT (textbooks)
- MIT Open Courseware (Math example textbooks)
- OER Commons (textbooks)
- OpenStax College – https://www.openstaxcollege.org/
- Open Book Publishers – http://www.openbookpublishers.com/
- Open Course Library – http://opencourselibrary.org/
- OpenLearn – http://www.open.edu/openlearn/
- Open Oregon – http://openoregon.org/resources/
- Open Textbook Library – http://open.umn.edu/opentextbooks/
- Project Gutenberg (historical Textbooks)
- Saylor Academy Open Textbooks – http://www.saylor.org/books/
- SUNY Textbooks – http://textbooks.opensuny.org/
- Teaching Commons Textbooks – http://teachingcommons.us/publication_type.html#textbooks_2
- The Orange Grove (textbooks)
- USF Scholar Commons Open Access Textbooks – http://scholarcommons.usf.edu/oa_textbooks/