OS

Android
android.com

Apps
google.com/mobile/android


Linux
linux.com
linux.org

Apple
iOS
Apple.com
apple.com/ios
apple.com/iphone
apple.com/ipad

Mac OS
Apple.com
apple.com/osx
apple.com/mac

Apps
apple.com/osx/apps/app-store.html

iCloud
apple.com/icloud
icloud.com


Windows
Microsoft.com
windows.microsoft.com

microsoft.com/surface