Wide Awake Pip - A speech-based game for toddlers and preschool kids
Math Games - Math Games is a website which kids in Preschool through 8th grade can practice math.
Mathquizily - Personalized math tests
GCompris - Educational Game for Children 2 to 10 years old.
Hellosaurus - Interactive mobile shows kids can play, not just watch
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.