Online Astronomy & Space Resources from Versant Power Astronomy Center

For Middle and High Schoolers:

Rocket Class from Instructables Aimed at the budding rocket enthusiast, aiming to keep things accessible by using mostly household items to create your own rockets.
Space-X Crew Dragon Docking Simulator Try your hand at the controls of the actual interface used by NASA astronauts to manually pilot the Dragon crew module to dock with the International Space Station!
Science Never Stops A series of videos with interesting experiments and information from the U.S. Space & Rocket Center.
Khan Academy Cosmology & Astronomy Online astronomy course for middle/high school students
Astronomical Society of Pacific K-12 Science Teachers Educational guides, hands-on activities, classroom resources, etc.
Zooniverse Citizen science projects including Galaxy Zoo (classifying galaxy pictures), Planet Hunters (searching for exoplanets), Solar StormWatch (tracking solar weather and effects on Earth) and numerous other astronomy ones. Additional citizen science projects in other disciplines like Arts, Literature, and Medicine.
Exploratorium Your weight on other worlds
NinePlanets.org Great overview of our solar system, including history, mythology and current knowledge/discoveries
National Radio Astronomy Observatory Radio telescopes look at the sky in a wavelength different from what we see with our eyes, and that opens up a whole new level of wonder and information. Radio telescopes linked together made the first image of a black hole possible.
Earth Day Climate & Environmental Activities