New apps are coming out all of the time. Here is a recommended list created in October 2013. This list includes math apps used in the classroom as well as apps that may be used at home. Some apps may require an account.
Website: http://www.khanacademy.org/
Free iPad app: https://itunes.apple.com/us/app/id469863705?mt=8&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/id469863705?mt=8&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=org.khanacademy.android
Free Android Tablet app: https://play.google.com/store/apps/details?id=org.khanacademy.android
Edmodo app: https://spotlight.edmodo.com/product/khan-academy,324527/
Paid iPad app: http://itunes.apple.com/us/app/fractions-app/id387434956?mt=8&uo=4&at=10l6SU
Paid iPhone app: http://itunes.apple.com/us/app/fractions-app/id387434956?mt=8&uo=4&at=10l6SU
Website: http://www.ixl.com/
Paid iPad app: https://itunes.apple.com/us/app/motion-math-hd/id410521340?mt=8&uo=4&at=10l6SU
Paid iPhone app: http://itunes.apple.com/us/app/motion-math/id392489333?mt=8&uo=4&at=10l6SU
Edmodo app: http://www.edmodo.com/publisher/motionmath
Paid iPad app: http://itunes.apple.com/us/app/factor-samurai/id441919897?mt=8&uo=4&at=10l6SU
Paid iPhone app: http://itunes.apple.com/us/app/factor-samurai/id441919897?mt=8&uo=4&at=10l6SU
Free iPad app: http://itunes.apple.com/in/app/tiny-chicken-learns-math/id490114227?mt=8&uo=4&at=10l6SU
Free iPhone app: http://itunes.apple.com/in/app/tiny-chicken-learns-math/id490114227?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/math-bingo/id371338715?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/math-bingo/id371338715?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/montessori-numbers-for-kids/id547209737?ls=1&mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/montessori-numbers-for-kids/id547209737?ls=1&mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/montessori-1st-operations/id627950311?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/montessori-1st-operations/id627950311?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/math-doodles/id526959716?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/connect-sums-math-doodles/id555216734?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/playful-minds-math-5-8-years/id449569846?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/playful-minds-math-5-8-years/id449569846?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/mathletics-student/id560955922?mt=8&uo=4&at=10l6SU
Website: http://www.mathplayground.com/
Free iPhone app: https://itunes.apple.com/us/app/geoboard-by-math-learning/id519896952?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/geoboard-by-math-learning/id519896952?mt=8&uo=4&at=10l6SU
Website: http://www.mathlearningcenter.org/web-apps/geoboard/
Google Chrome app: https://chrome.google.com/webstore/detail/geoboard-by-the-math-lear/gaakmmdiopnmcenkojohldanladpajak
Paid iPhone app: https://itunes.apple.com/us/app/sums-stacker/id343251346?mt=8&uo=4&at=10l6SU
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
Free iPad app: http://itunes.apple.com/in/app/tiny-chicken-learns-currency/id511250020?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/kindergarten-common-core-sight/id446633408?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/kindergarten-common-core-sight/id575641167?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/kindergarten-common-core-sight/id446633408?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/kindergarten-common-core-sight/id575641167?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/kindergarten-common-core-math/id666380499?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/kindergarten-common-core-math/id666380499?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/kindergarten-common-core-math/id480538911?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/kindergarten-common-core-math/id480538911?mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/app/math-champ-challenge-common/id566463831?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/app/math-champ-challenge-common/id566463831?mt=8&uo=4&at=10l6SU
Website: http://www.mathalicious.com/
Paid iPad app: https://itunes.apple.com/us/app/ordered-fractions-compare/id592036890?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/ordered-fractions-compare/id592036890?mt=8&uo=4&at=10l6SU
Free iPad app: http://itunes.apple.com/us/app/fractions-by-brainingcamp/id471353363?mt=8&uo=4&at=10l6SU
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
Paid iPhone app: https://itunes.apple.com/us/app/1+1-dice/id602412524?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/1+1-dice/id602412524?mt=8&uo=4&at=10l6SU