Check out these great websites for general science resources!

Good site for 3rd and 5th grade earth science.
NASA website

Earth and Moon Viewer - Awesome website that shows live... yes live, images of the Earth and Moon. Great for viewing night side of Earth and understanding time zones, day and night, sunrise/sunset, etc.
http://www.fourmilab.ch/earthview/vplanet.html

Cell Size and Scale - Good website to show the relative sizes of microscopic objects. Use scroll bar below to zoom.
http://learn.genetics.utah.edu/content/begin/cells/scale/

Earthquakes in Southern California - We live in earthquake country! Observe recent, up to date information on earthquakes in our state.
http://www.data.scec.org/
Tasa Earth Science Illustrations - Great website with illustrations and animations for 6th Grade Plate Tectonics
www.tasaclips.com

World Population Clock - How many people are there in the U.S.? How often do people die? How often is a new kid born?
www.census.gov/population/www/popclockus.html