Astronomy Photo of the Day

Astronomy Picture of the Day : NASA
As a link-of-the-day site, I'm also drawn to other sites that publish on a daily basis.
NASA's Astronomy Picture of the Day produces stunning space photos day after day, with an explanation of what you're looking at. There's also an space photo archive, with daily photos that go back to June 15, 1995.

Thanks to Wired's Geek Dad blog for mentioning