Free Mac program: http://www.geogebra.org/cms/download
Free Windows program: http://www.geogebra.org/cms/download
Google Chrome app: https://chrome.google.com/webstore/detail/geogebra/bnbaboaihhkjoaolfnfoablhllahjnee
Google Chrome app: https://chrome.google.com/webstore/detail/bhdheahnajobgndecdbggfmcojekgdko
Website: https://www.desmos.com/
Edmodo app: http://www.edmodo.com/publisher?uid=3382251
Free iPad app: https://itunes.apple.com/us/app/graphing-calculator-by-desmos/id653517540?mt=8&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/graphing-calculator-by-desmos/id653517540?mt=8&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.desmos.calculator
Free Android Tablet app: https://play.google.com/store/apps/details?id=com.desmos.calculator