HoDoKu - HoDoKu is a sudoku helper written in Java and available in English and German.
GCompris - Educational Game for Children 2 to 10 years old.
Minimal Sudoku - Minimal Sudoku is an easy to use, clutter-free classic sudoku game which is designed for iOS 7.
Tux Paint - Tux Paint is a free, award-winning drawing program for children ages 3 to 12 (for example, preschool and K-6).
Yasminoku - Sudoku game and solver totally written in DHTML.
I Know It - "I Know It" is an online game for practicing primary-level math concepts.