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.academicmerit.com/
Website: http://www.claco.com/
Website: http://learnzillion.com/
Website: http://www.studysync.com/
Google Apps for Education app: https://www.google.com/enterprise/marketplace/viewListing?productListingId=6546+12747060046611723303
Website: http://www.learnboost.com/
Google Chrome app: https://chrome.google.com/webstore/detail/learnboost/lfbigbedbdencpbioocekehcblgokpno
Website: http://powermylearning.org/learn/learning-games-activities
Free Android Phone app: https://play.google.com/store/apps/details?id=com.socrative.teacher
Free iPad app: https://itunes.apple.com/us/app/teacher-clicker-socrative/id477620120?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/teacher-clicker-socrative/id477620120?mt=8&uo=4&at=10l6SU
Website: http://www.socrative.com/
Edmodo app: http://www.edmodo.com/publisher/socrative
Google Chrome app: https://chrome.google.com/webstore/detail/socrative-teacher/ofajgnplnindhnhnconjocimijjifaln?hl=en