The Google Apps Education Training Center is an online learning environment dedicated for educators and students to learn how to effectively use Google Apps in an educational context. In other words, it provides training materials to learn how to use Google Apps in education.
While you don't need a Google Apps account to use this site, it is recommended so that you can experience what you learn. Of course, if you have a Google account you can use many of the apps anyway.
This is a good resource for teachers and students whose school system uses Google Apps or for any teacher or student who uses Google's applications for school.