Website: https://www.google.com/
Free iPad app: https://itunes.apple.com/us/app/google-search/id284815942?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/google-search/id284815942?mt=8&uo=4&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.google.android.googlequicksearchbox
Google Chrome app: https://chrome.google.com/webstore/detail/google-search/coobgpohoikkiipiblmjeljniedjpjpf
Website: http://www.bing.com/
Free iPhone app: https://itunes.apple.com/us/app/bing/id345323231?mt=8&uo=4&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.microsoft.bing
Paid iPad app: https://itunes.apple.com/app/wolframalpha/id334989259?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/app/wolframalpha/id334989259?mt=8&uo=4&at=10l6SU
Paid Android Phone app: https://play.google.com/store/apps/details?id=com.wolfram.android.alpha
Paid Android Tablet app: https://play.google.com/store/apps/details?id=com.wolfram.android.alpha
Website: http://kids.yahoo.com/reference/encyclopedia