Interesting reading if you would like to know more about early childhood education:
And another focused on childhood development:
NAEYC: A great resource for any teacher or parent!
Scholastic- resources for the classroom: http://www2.scholastic.com/browse/teach.jsp
NIST Education Resources on the Metric System (lots of free info and materials for teachers and students):
KIDS.gov (official kids portal for the US Government):
Federal Resources for Educational Excellence (aka FREE):