Website: http://www.minecraft.net/
Paid Mac program: https://minecraft.net/download
Paid Windows program: https://minecraft.net/download
Website: http://www.classcraft.com/
Free iPad app: https://itunes.apple.com/us/app/classcraft/id968213964?mt=8&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/classcraft/id968213964?mt=8&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.classcraft.android
Free Android Tablet app: https://play.google.com/store/apps/details?id=com.classcraft.android