Exploring Planets in the Classroom http://www.spacegrant.hawaii.edu/class_acts/index.html Hands-on science activities from University of Hawaii. Mostly Planetary Science and Geology.
Live from Earth and Mars http://www-k12.atmos.washington.edu/k12/index.html More than just activities, also includes workshop materials and teacher/student projects.
Mars Exploration Curriculum http://mars.jpl.nasa.gov/education/modules/webpages/curriculumwelcomepage.htm More activities about Mars
Galileo Mission Education Modules http://www.jpl.nasa.gov/galileo/sepo/webflier.html Activites relating to Jupiter and it's moons.
Comet Recipe http://www.noao.edu/education/crecipe.html Make a comet in your classroom.
Great site for Astronomy Activities and Background Info from the Lunar and Planetary Institute: http://www.lpi.usra.edu/education/resources/
Astronomy with a Stick http://www.nsta.org/publications/interactive/aws-din/aws.aspx Solar Astonomy
NASA/MSU-Bozeman CERES Project Educational Activities http://btc.montana.edu/ceres/html/EdActivities.html For grades K-12 following the NASA themes.
NOAO Image Gallery http://www.noao.edu/image_gallery/
Astronomy Picture of the Day http://antwrp.gsfc.nasa.gov/apod/astropix.html A new astronomy-related image every day. Plus archives of all previous images.
LPI Slide sets http://www.lpi.usra.edu/publications/slidesets/lpislides.html These can be ordered as slides for a fee or downloaded as .gif files for computer use.
Multiwavelength Milky Way http://mwmw.gsfc.nasa.gov/mmw_edu.html Images of our galaxy in different wavelengths (colors).
PlanetScapes http://planetscapes.com/ Views of the Solar System - lots of images with descriptions.
NASA Planetary Photojournal http://photojournal.jpl.nasa.gov/ Almost every image ever taken by a NASA spacecraft can be found here.
NASA- JSC Digital Image Collection http://images.jsc.nasa.gov/ Images taken from shuttle missions and press release images from the manned space program.
Galileo http://www.jpl.nasa.gov/galileo/index.html Nearly finished mission to Jupiter and its moons.
Mars Global Surveyor http://mars.jpl.nasa.gov/mgs/
2001 Mars Odyssey http://mars.jpl.nasa.gov/odyssey/
Near Earth Asteroid Rendezvous (NEAR) http://near.jhuapl.edu/ Succesful mission to an asteroid.
Cassini-Huygens http://www.jpl.nasa.gov/cassini/ Mission on its way to study Saturn.
Kepler Mission http://www.kepler.arc.nasa.gov/ Extra-solar planet search mission.
SETI Education http://www.seti.edu/education/ Education webpage from the Search for Extraterrestrial Intelligence.
Bad Astonomy http://www.badastronomy.com/ Actually a GOOD Astronomy page that explains what is bad about astronomy in popular media: movies, television, etc.
astronautix.com http://www.friends-partners.org/partners/mwade/index.htmUS/Russian space missions, with an emphasis on manned missions and spacecraft.
The Nine Planets http://seds.lpl.arizona.edu/nineplanets/nineplanets/nineplanets.htmlTHE place to go for information about the solar system.
How things work http://rabi.phys.virginia.edu/HTW/A physicist answers you questions.
Support Network http://spacescience.nasa.gov/education/ecosystem.htm Addresses of regional NASA contacts for Public Outreach Support.
Astronomical Society of the Pacific http://www.astrosociety.org/education.html Home of Project ASTRO.
SSDOO Education Outreach Page http://ssdoo.gsfc.nasa.gov/education/education_home.html Launches, news and resources from the Space Science Data Operations Office of NASA/Goddard Space Flight Center.
Education Resources Catalog http://www.lpi.usra.gov/education/ERC/resources.html
NASA CORE http://core.nasa.gov/ Central Operation of Resources for Educators.
Challenger Center http://www.challenger.org/ Challenger Center for Space Science Education.
Students for the Exploration and Development of Space http://www.seds.org/
STScI Public Information http://oposite.stsci.edu/pubinfo/ Includes links to Hubble images.
NASA Quest http://quest.nasa.gov/space/teachers/liftoff/ Written guides to accompany the Liftoff to Learning video series.
LPI Education Resources http://www.lpi.usra.edu/education/education.html List of programs, products and resources from the Lunar and Planetary Institute.
NASA Spacelink http://www.nasa.gov/audience/foreducators/index.html An Aeronautics and Space Resource for Education.
Windows to the Universe http://www.windows.ucar.edu/ Web site about Earth and Space sciences. Ingludes games, art, data, and cool stuff.
SSI Education http://www.spacescience.org/Education/1.html Activities, information, and resources from the Space Science Institute.
Universe in the Classroom http://www.astrosociety.org/education/publications/tnl/tnl.html Teacher's Newsletter from the Astronomical Society of the Pacific.
Hoku http://www.cfht.hawaii.edu/Reference/Library/hoku/ Newsletter for Educators and Parents.
Sky and Telescope Magazine http://www.skypub.com/
Astronomy Magazine http://www.astronomy.com/asy/default.aspx
Imagine the Universe http://imagine.gsfc.nasa.gov/index.htmlActivities and other resoures for high school.
Star Child http://starchild.gsfc.nasa.gov/docs/StarChild/StarChild.html A learning center for young astronomers, 14 and under.
Mars Academy http://www.marsacademy.com/ Activities centering around colonization of Mars.
New Mars http://www.newmars.com/ Journal of the Mars Society
Mars Education http://mars.jpl.nasa.gov/classroom/ From JPL, maker of Mars missions.
Expanding your Horizons http://www.expandingyourhorizons.org/ Nation-wide program for junior high school girls.
The Sacred Sky of the Navajo and Pueblo http://arcturus.pomona.edu/sw/Navajo.griffith.essay2.html