NASA for middle-school students http://www.nasa.gov/audience/forstudents/5-8/features/index.html
National Geographic for Kids http://www.nationalgeographic.com/kids/
The Scientific Method (Interactive) http://biology.clc.uc.edu/Courses/bio104/sci_meth.htm
Geography 4 Kids Geography 4 Kids
The Water Cycle (Interactive) http://www.epa.gov/ogwdw/kids/flash/flash_watercycle.html
Cells ALIVE! http://www.cellsalive.com/
EdHeads - Activate Your Mind!!! http://www.edheads.org/