Website: http://www.ck12.org/
Free Android Phone app: https://play.google.com/store/apps/details?id=org.ck12.app.practice
Free Android Tablet app: https://play.google.com/store/apps/details?id=org.ck12.app.practice
Google Chrome app: https://chrome.google.com/webstore/detail/ck-12/ilmbnmigihncgeckjgmkehcgkdeohkhl
Free iPad app: https://itunes.apple.com/us/app/ck-12-free-fun-way-to-learn/id909343639?mt=8&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/ck-12-free-fun-way-to-learn/id909343639?mt=8&at=10l6SU
Website: http://www.youtube.com/teachers
Paid iPad app: https://itunes.apple.com/us/app/book-creator-for-ipad-create/id442378070?mt=8&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/book-creator-free-make-books/id661166101?mt=8&at=10l6SU
Google Chrome app: https://app.bookcreator.com/sign-in
Website: https://bookcreator.com/
Free Windows program: https://app.bookcreator.com/sign-in
Free Mac program: https://app.bookcreator.com/sign-in