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.

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.

The Truth About 2012: Ed Krupp from Griffith Observatory debunks claims the world will end.

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."

The Universe Adventure. A fabulous introduction to cosmology and the Big Bang Theory.

The Particle Adventure. An introduction to the world of quarks, electrons, and neutrinos from the same people that put together the Universe Adventure.

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.