I'll take this opportunity to shamelessly plug APOD; Astronomy Picture of the Day.
there's a lot of sites I visit daily, but this has been one of my favorites for a long time. the link is also in my sig.
the archive for all previous APODs is here. and most of them are massive wallpaper size.
they have something unique every single day of the year.
2014 February 8...
I am going to start visiting this site.