These are other free educational softwares:

• Gcompris provides a lot of activities (more than 70) for children from 2 to 10 years old.
• Childsplay provides few activities and is based, like Pysycache, on the pygame library

And some programs that bring together some nice educational softwares:

• The softwares pack of
  terrier by the AbulEdu team
• ofset.org
• skolelinux