Foothill Astronomy Instructor Andrew Fraknoi has a Facebook page for astronomy news called "Andrew Fraknoi (The AstroProf)": http://www.Facebook.com/Fraknoi
The Astronomical Society of the Pacific, with headquarters in San Francisco, has many programs of interest to those with an interest in astronomy. Learn more at: http://www.astrosociety.org
The SETI Institute is a scientific and educational organization devoted to the search for life in the universe: http://www.seti.org
National Optical Astronomy Observatories Image Gallery: http://www.noao.edu/image_gallery/ (This growing archive shows images taken with the many telescopes that are part of the National Optical Astronomy Observatories.)
"Seeing in the Dark" (A PBS television program about the joys of amateur astronomy, with good introductory resources for new hobbyists): http://www.pbs.org/seeinginthedark/
Sky & Telescope Magazine: http://skyandtelescope.com (a magazine for astronomy hobbyists, with many good articles and primers at their site)
"Windows to the Universe": http://www.windows2universe.org/ (a rich site for younger readers and beginners, full of space and earth science information)
The Planetary Society: http://www.planetary.org (this national organization supporting the exploration of the planets has a colorful site with good background information about the solar system)