GCompris - Educational Game for Children 2 to 10 years old.
Tux Paint - Tux Paint is a free, award-winning drawing program for children ages 3 to 12 (for example, preschool and K-6).
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.
TuxMath (Tux of Math Command) - Tux, of Math Command, AKA TuxMath, lets kids hone their arithmetic skills while they defend...
Etoys - Etoys is an educational tool for teaching children powerful ideas in compelling ways.
Get Sudoku - Get Sudoku is an interactive sudoku solver.