Annenberg Learner: Interactives and Video Courses

NOAA

 Population Education - Resources to help teach growth

National Energy Education Development (NEED) - Energy Infobook Activities for general energy information, energy sources, electricity, and conservation. 

Middle School Chemistry - Full Lessons from ACS

Daily Science History - On This Day

NASA - Science for Kids

Science Articles - Time for Kids

Frontiers for Young Minds - Open access peer reviewed scientific articles written by kids and edited by kids.