There is a great place were astrophotografers keep their best photos. Have a look at AstroBin were amazing photos are stored and shared. Browse through the pictures or go directly to the Image of the day. A somewhat related service is Astrometry where you can submit your picture to find out what part of the sky it shows.
Another place taking a lot of pictures of the sky is the Sloan Digital Sky Survey. SDSS is mapping the sky and their pictures are used by Google and Microsoft among others. Go to the SkyServer or the gallery.
NSSDCA Photo Gallery (not necessarily taken from Earth but a great gallery)