Cruising through Infosthetics the other day, I ran into The Whole Internet. This is a map of all 4,294,967,29 IPv4 addresses, broken down by owner, using a rather smooth image-scaling program that makes it quite navigable. Picked out in red are all the IP addresses listed in the Spamhaus XBL, in my opinion one of the more reputable blocklist clearing houses around.
My one criticism of this interface, of course, is that there’s no clear mechanism for centering on a particular IP other than manually clicking around until you find something close.