Physics: Astronomy & Astrophysics

A joint publication of the U. S. Nautical Almanac Office, United States Naval Observatory (USNO) and Her Majesty's Nautical Almanac Office (HMNAO), United Kingdom Hydrographic Office (UKHO). It contains the tables giving the positions of astronomical objects, such as the the Sun, Moon, planets and satellites, data for eclipses and other astronomical phenomena for a given year.

A Wiki from the United States Naval Observatory that provides information on the sun, moon, day length, eclipses and other astronomical phenomena.

Provides links to several maps of the Universe produced at various scales (in light years).

A linked list of past, current and planned astronomical missions from the National Aeronautics & Space Administration (NASA).

While there are now only 8 planets (and several dwarf planets), this site is still useful. It provides a survey of information about the mythology, history and science of the planets, moons and other objects in the Solar System.

STSI is the organization that oversees science programs, grants, planning, scheduling, and outreach activities for the Hubble Space Telescope. It also archives and distributes data for all of NASA's optical/UV missions, including the Hubble Space Telescope.

AstroWeb used to have a list of telescopes, but it is no longer active. However, Wikipedia's article on telescopes has a good list of the types of telescopes with links to separate lists of each type of telescope. The lists also include links to individual telescopes.