Shamelessly taken from r/space: http://www.reddit.com/r/space/comments/2p6gy7/heres_a_viewer_for_an_amazing_150000_megapixel/
Very neat!
Also check out the Hubble eXtreme Deep Field (full-size jpg). It's an image of a dark section of sky far away from the Milky Way. Each speck of light is an entire galaxy!!