Google Chrome app: https://chrome.google.com/webstore/detail/diigo-bookmark-archive-hi/oojbgadfejifecebmdnhhkbhdjaphole
Mozilla Firefox extension: https://addons.mozilla.org/en-US/firefox/addon/diigo-web-highlighter-and-stic/
Free iPad app: https://itunes.apple.com/us/app/diigo/id417202559?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/diigo-offline-reader/id335006600?mt=8&uo=4&at=10l6SU
Website: http://www.diigo.com/
Free Android Phone app: https://play.google.com/store/apps/details?id=com.google.android.apps.docs
Google Chrome app: https://chrome.google.com/webstore/detail/google-drive/apdfllckaahabafndbhieahigkjlhalf
Free iPad app: https://itunes.apple.com/us/app/google-drive/id507874739?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/google-drive/id507874739?mt=8&uo=4&at=10l6SU
Website: http://drive.google.com/
Free Android Tablet app: https://play.google.com/store/apps/details?id=com.google.android.apps.docs
Free Mac program: https://www.google.com/drive/download/
Free Windows program: https://www.google.com/drive/download/
Website: http://moodle.org/
Website: http://www.avatarclassroom.com/