Some useful links:
More will be added, and suggestions are always welcome.
On-line education/outreach resources:
- Caltech astronomy outreach
- JPL (many popular astronomy links)
- Sky & Telescope Online Astronomy Links
- AstronomyOnline
- Griffith Observatory
- StarDate
- APOD educational links
- SETI Institute
- Astrobiology links from SDSU
Pretty pictures:
- Astronomy Picture of the Day
- Hubble Space Telescope Gallery
- James Webb Space Telescope images
- Euclid Mission Gallery
- ESO Gallery
- CFHT Image Gallery
- NOIRLab Image Gallery
- NRAO Image Gallery
- AstroPix at IPAC
- G. Paglioli's astronomy pictures
Observatories and space missions:
- NASA public website
- European Southern Observatory
- James Webb Space Telescope
- Hubble Space Telescope
- Rubin Observatory (LSST)
- NOIRLab
- National Radio Astronomy Observatory
- Palomar/COO
- Keck
- OVRO
- Spitzer Space Telescope
- Chandra X-ray Observatory
- Fermi Gamma-ray Space Telescope
- GAIA mission
- Planck mission
Miscellaneous:
- Ethan Siegele blog, "Starts With a Bang"
- Sky & Telescope list of astronomy blogs
- Astrobites
- Khan Academy Cosmology and Astronomy
- Motion Mountain free physics textbooks