This xkcd comic is just way too cool to be left unblogged:
Needless to say, due to its ginormous size I needed to cut off the middle part (one of the beauties of its CC-by-nc license), so make sure to click on the picture to see it in all its beauty.
Randall Munroe made a map of the observable universe, from top to bottom, on a logarithmic scale. I love the details ("Eris: All hail discordia!"--Eris is the Greek goddess of strife, or Cory Doctorow in a balloon, or Pluto (not a planet, neener neener)...). It's also cool how funny the buildings look due to the scale.
It's also available as a poster!