NASA Astronomy Picture of the Day
Few Web sites inspire awe of space and the stars than NASA's formidable online image archive. The best starting place is the NASA Astronomy Picture of the Day site, which stands apart because of the descriptions supplied with each photo by professional astronomers. The images here are breathtaking, with examples such as "clouds of interstellar dust and gas blossoming 1,300 light-years away in the fertile star fields of the constellation Cepheus".
NASA Images / NASA Featured Images and Galleries
For more images like this, the NASA Images site has photos of Earth, solar systems and astronauts, and the NASA Featured Images and Galleries site are a must-visit.
HubbleSite
Possibly the most surreal of all though are the photo albums of nebulae, galaxies and stars on the HubbleSite, which are truly spectacular.
GalaxyZoo
For the real enthusiast Galaxy Zoo gives you a unique opportunity to assist researchers in classifying galaxies, a task that it turns out computers have been unable to do reliably.
The Neave Planetarium
There are two other sites that also stand out for their ability to let you explore the stars: The Neave Planetarium gives you a star map in your browser - click a star to see its constellation and how many light years away it is.
Microsoft's WorldWide Telescope
This site takes online planetariums to another level, with guided tours and actual images from telescopes as you explore. The drawcard are guided tours of the stars created by astronomers.
Also see our guide to Astronomy 101 for the home: view the planets in stunning detail on your PC