Astronomy:

Ask an Astrophysicist

NASA

NASA Online Activities

NASA Multimedia

NASA Education Program

Windows to the Universe

Stardate Online

ScienceMaster - Space Science

Solar System Simulator

The Nine Planets

Space Science Hotlist

Solar System Test 

Earth From Space 

Hubblesite Gallery

The Best of Hubble Space Telescope

Images from Spitzer Space Telescope

Geology:

Fault Animations

Earthquakes

Idaho Geological Survey

Real-Time Earthquakes

Volcanoes Online

Education Module

Earth System Science Course

Geology Labs Online

Glossary of Geologic Terms

Volcano World

USGS

Earth Science Using the Internet

Earthquake Exploration
 

General:

Online Articles - Web Based Learning

Earth Science Online Course Syllabus

Weather and Climate For Teachers

Earth Science Lessons

Earth Science Resources

Lesson Plans and Curriculum

Science Resources

Earth Science Education Products and Resources

Earth Science Teaching Resources

Geological Society Teaching Resources

Earth Science/ Geography Education Listings

Earth Science Emporia State

Science Resources

Digital Library for Earth Science Education
 

Weather:

GOES Hot Stuff

Project Storm

Weather Education Resource Links

Curriculum Correlation Documents for All About Meteorology

Penn State Lesson 9 Meteorology

DataStreme Atmosphere

Water in the Earth System

DataStreme Ocean