I Know It - "I Know It" is an online game for practicing primary-level math concepts.
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.
GCompris - Educational Game for Children 2 to 10 years old.
Math Games - Math Games is a website which kids in Preschool through 8th grade can practice math.
Tux Paint - Tux Paint is a free, award-winning drawing program for children ages 3 to 12 (for example, preschool and K-6).
Cool Math Endless Run - Cool Math Endless Run is a monster math game and an endless run adventure.