Astronomical observation and information online-calculator . Allows you to make your own calendar with satellites, asteroids, comets, planets, sun, and moon. See renderings of solar eclipses, and the planets. Calculates conjunctions and even ISS transits of the Sun and Moon.

Excellent way to get the current viewing conditions in your area. We use the ones for Louisville, KY and Chandler, AZ.

All kinds of detailed information about eclipses and transits.

A great place to see what the exact current sunspot condition of the sun is.

Handy site for seeing what comets are currently visible and how bright they are.

Stephen Wolfram's amazing computational knowledge engine. I read that this site is operated from 10,000 servers. That's some computing power.

Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

NASA's official Hubble Telescope site. Has lots of great pictures and interesting information.