Paid iPhone app: http://itunes.apple.com/us/app/boggle/id327836363?mt=8&uo=4&at=10l6SU
Website: http://www.ixl.com/
Free iPad app: https://itunes.apple.com/us/app/5-dice-order-operations-game/id572774867?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/5-dice-order-operations-game/id572774867?mt=8&uo=4&at=10l6SU
Website: http://freerice.com/