Astronomy Now (online news service for astronomical topics)
Spaceflight Now (online news service for current topics in the space program)
Nature Magazine (International weekly journal of science)
Science Magazine
"Science News" Magazine
Astronomy Magazine News (Current news from one of the largest amateur astronomy magazines)
Sky and Telescope Magazine News (Current news from one of the largest amateur astronomy magazines)
Today at NASA (current news releases from the National Aeronautics and Space Administration)
Space.com (space related news, information, education, entertainment, games, science fiction and a kids' channel)
NightSky (a terrific resource for current astronomical events)
Spaceviews.com (space news online)
SpaceDaily.com ("Your Portal to Space")
MarsDaily.com ("Your Portal to Mars")
Astronomy and Astrophysics Links (very comprehensive set of links covering a huge range of topics)
NASA TV (watch a live broadcast of NASA TV)
   

Skymaps.com (print out your very own copy of the current month's star chart.  Each chart comes with a brief description of what is visible and when - and its FREE!)

 

Astronomy Picture of the Day (great site to see a different picture each day. Each picture comes with a description that will take you places on the internet you have never gone before!)
Sky & Telescope Magazine's SKY AT A GLANCE
STAR DATE Magazine Online (Monthly Sky Almanac)
THE OLD FARMER'S ALMANAC ONLINE (Daily Sunrise/Sunset and Moonrise/Moonset times are listed - just enter your city/state and press go!  Very useful indeed)
Current Phase of the Moon (this site will tell you the current phase of the Moon)
Daily Solar Images:
   
Current X-ray image of the Sun (from SOHO)
    Current Ultraviolet image of the Sun (from SOHO)
    Current white-light image of the Sun's corona (HAOMLSO Hawaii)
    Current image of the Sun showing sunspots (from Stanford University)
Where are the planets right now? (Solar System Live program shows you the exact location of each planet for today's date)
Spaceweather.com (Science news and information about the Sun-Earth environment)
Current Space Weather (monitor real time data related to solar activity)
View the most recent auroral activity (i.e. where are the "northern lights" most active lately)
J-Track (track earth orbiting satellites including the Hubble Space Telescope and more!  Using this website you can learn when to go outside to actually witness a particular satellite pass overhead! Very cool!!)
Human Space Flight (Check this NASA website to find opportunities to witness the Space Shuttle or the International Space Station pass overhead)
Heavens Above (This is the best place to go to learn when to go outside and see when man-made Earth orbiting satellites will pass overhead, the current positions of the bodies in our solar system and more.
   
   
Hubble Space Telescope Images (Latest HST images and video released to the public plus an archive of all previously released stuff)
Hubble Heritage Project (some of the best HST images collected into a cool looking website!)
Recent Supernovae Webpage (view images of recently detected supernovae)
Astronomy Picture of the Day (great site to see a different picture each day. Each picture comes with a description that will take you places on the internet you have never gone before!)

 

Planetary Photojournal (JPL's database of solar system images from the many different historical exploratory missions)
The Galaxy Catalog (a bounty of images of galaxies in different image formats)
Views of the Solar System (Image and Animation Index)
   
   
SETI Institute (Search for Extra-Terrestrial Intelligence - the scientific search for life in our universe)

 

Space Adventures (Space tourism?? It might be closer than you think... just bring money, lots of money!)
Nick Strobel's Website (tutorials on a wide variety of astronomical topics)
The Nine Planets (lots 'o good information about the solar system hosted by SEDS)
LAUNCH OF DOOMED MARS POLAR LANDER (QUICKTIME VIDEO) (Ever want to know what it would look like to hitch a ride on a Delta II rocket?  This little camera was mounted on the side and shows a video of the liftoff until until main engine cut off.  Warning: this is a HUGE video file, but it is worth the wait!)
An imaginary conversation with the planet Pluto
JPL's Solar System Simulator (check it out...it's really cool!)
Tour the Universe (a VRML program that will allow you to zip around the universe... really cool!!)
The Official US Time (Official time as kept by NIST)
The Astronomy Cafe ("the website for the astronomically disadvantaged")
Apollo Lunar Surface Journal (everything you've ever wanted to know about the Apollo missions to the Moon)
The Origin of the Moon (a description of the origin of our nearest celestial neighbor)
Phil Plait's BAD ASTRONOMY (debunk bad astronomy on this very informative website)
Space Calendar (space related activities and anniversaries for the current year)
A View From the Back of the Envelope (okay, so it isn't REALLY an astronomical page, but it is pretty useful and cool...)
Google Earth (find a satellite image for just about anyplace in the U.S. and some other parts of the world)
  Where is M13? (this very cool FREE program will help you visualize where popular astronomical objects are located within the galaxy - relative to the Sun's location)
  The Constellations (comprehensive information about the 88 different constellations)
  The Names of the Stars (and the meaning of the names)
  Stellarium (a terrific FREE planetarium program that shows the obects of the sky - day or night.  Did I mention that it is FREE?)
   
  Palomar Observatory Hale 200-inch Telescope Webcam (Live images of activity inside the dome of the Hale Telescope)
The Night Sky Live (Live images of the night sky seen from various observatories around the world via CONCAM)

 

North Pole Webcam (see a live image of the North Pole)
South Pole Webcam (see a live image of the South Pole)