GCompris - Educational Game for Children 2 to 10 years old.
childsplay - Childsplay is a collection of educational activities for young children and runs on Windows, OSX, and Linux. Childsplay can be used at home, kindergartens and pre-schools.
Akribian - Akribian turns children into Mathemagicians with their new iOS app, Count on me!
I Know It - "I Know It" is an online game for practicing primary-level math concepts.
Cool Math Endless Run - Cool Math Endless Run is a monster math game and an endless run adventure.
DragonBox Algebra - DragonBox Algebra 5+ - The educational game that secretly teaches you algebra.