Astronomy, Astrophysics, Galactic, Solar System (Planetary), Spaceflight and Exploration, Stargazing, Stellar (hosted by the iSchool at Drexel, College of Information Science and Technology)
IfA Star Chart of the Month - Customized for Hawaiian skies, includes moon phases and planets' positions (Institute for Astronomy, University of Hawaii)
*Data Services - Sun and moon rise/set times, moon phases, eclipses
&
transits,
seasons, positions of selected celestial objects, and other data
* Time Service Department
- Official time source for the Dept. of Defense (DoD), the Global Positioning System
(GPS), and the standard of time for the U.S.
Your Sky - Interactive
planetarium : produce maps for any time and date, viewpoint and observing location
Astronomy Facts - Astronomers, Nearest Stars, Constellations, Messier Objects, Obsolete Constellations, and more (Shane Horvatin, Abrams Planetarium, Michigan State University)
Astronomy Thesaurus - Click on the British flag to get started in English. One you select a term, you'll see it in French, German, Italian, and Spanish at the top of the page. Entries show Use, Use For, Broader Term, Narrower Term, Related Term (although most entries don't have all categories). There is also a hierarchical listing.
Birthday Star Chart - Find a star that is your age in light years from Earth
Journey through the Galaxy - A "mini-net" of pages that explore our solar system, stars, extra-solar planets, theories about the universe, and exploration of space
physics.org - "The best physics resources, all in one place" hosted by Institute of Physics