Stellarium
Celestia

Epo's Chronicles - A web comic from the outreach group at Sonoma State - very cool!
Sky & Telescope
Astronomy
Star Date
Universe Today
SPACE.com
The Astronomy Cafe
Earth and Sky
Bad Astronomy

Space Adventures - Considering space tourism? Some have done it already!
American Astronomical Society
The Planetary Society - The largest nonprofit, nongovernmental space advocacy group on Earth.
SETI Institute - The Search for Extraterrestrial Intelligence.
SETI@home - Grid computing project that allows you to help reduce and analyze some of the SETI data.
U.S. Naval Observatory
San Diego Amateur Astronomers
Griffith Observatory
Los Angeles Astronomical Society
List of clubs in southern California (from the Los Angeles Astronomical Society)
Riverside Telescope Makers' Conference (RTMC) annual Nightfall.

The Universe Adventure - A cool project funded in part by NSF, DOE, LBNL, and the Bechtel Corporation.
Online tutorial on using an SC001 chart.
Heavens Above - Satellite, HST, ISS, iridium flare, etc. predictions for your area.
SkyView
Satellites
Excellent articles for beginners from Sky and Telescope.
Star-finding with a planisphere.
Skymaps - Free downloadable star chart for each month.
USNO Data Services - Sun/Moon, Rise/Set, Twilight, Eclipses, Transits, other astronomical phenomena.
Powers of 10
Retrograde Motion Animated Demonstration
Foucault Pendulum and the rotation of the Earth (from the California Academy of Sciences)
• Diagramming the plane of oscillation on the floor.
• How position on the Earth affects the apparent change of the pendulum's plane of oscillation.
Visible spectra of the elements, absorption and emission.
Windows to the Universe
Cosmic Evolution - from the Wright Center for Science Education at Tufts University.
Hubble Deep Field
SOHO - The Solar and Heliospheric Observatory.
3D Guide to the Galaxy by NASA's PlanetQuest.
Moon Map
Astrophysics Links and Resources
Table of Constellations
SpaceWeather.com
NASA's Planetary Photojournal.
The Nine Eight Planets - A Multimedia Tour of the Solar System.
JPL Solar System Simulator
Time.gov - The official US time.
A View from the Back of the Envelope
Runaway Universe - From NOVA.
Night Sky Live