The Astrochymist This independently maintained site contains the name, formula, original report and date of detection, and location for each chemical found in space.
Astrobiology Web Maintained by a private corporation, this site covers recent news, related websites, and official reports by NASA, NIH, and other authoritative sources. Coverage beyond the search for life includes astrochemistry, astrophysics, and the effect space has had on life on Earth.
NASA The official site of the National Aeronautics and Space Administration features age specific resources including text, images, video, and various multimedia applications. The site also covers the most recent news and developments in the field.
NASA Images A new online archive of hundreds of thousands of NASA images.
HubbleSite The Space Telescope Science Institute maintains this site which covers the lastest news and discoveries from the Hubble Telescope as well as galleries of it's previous pictures.
Other Physics Subtopics
The Elegant Universe PBS and NOVA present The Elegant Universe, a three hour streaming program and accompanying website explaining string theory to the masses.