Astronomy Picture of the Day. Outstanding sky images taken by the Hubble Space Telescope, interplanetary spacecraft, observatories on Earth, and amateurs.
Hubble Heritage Site. The best of the Hubble Space Telescope.
SpaceImages from ESA (European Space Agency)
SkyandTelescope.com. The website of Sky and Telescope magazine. Astronomy news and observing highlights for the amateur astronomer.
Bad Astronomy: Phil Plait's intriguing expose of fallacies, misconceptions, and outright frauds.
Full Moon and Lunar Effects on behavior. A discussion of the controversial idea that the Full Moon is associated with increased crime, craziness, or accidents.
Class Action. This is the website that has the practice questions we use in class.
PhET. Fun, interactive physics and astronomy simulations. Astro 25 students : check out "Blackbody radiation."
Physics 2000. An illustrated, friendly explanation of physics concepts, including gravity, electromagnetism, and spectra.
Atmospheric Optics All about rainbows, sundogs, and halos: strange and beautiful things to see in the atmosphere.
History of the World in 18 Minutes by historian David Christian.