The nixCraft blog has an article about a very interesting map of the IPv4 address space from the Measurement Factory as part of the RouteViews project. The most recent map looks like this:
The map is very detailed (the above image is only a small version) and is available from CafePress as a full-size poster.
The map shows the IPv4 space as understood by the BGP routing protocol. The black areas are unroutable (at least from the Measurement Factory’s location at the University of Oregon) and the gray areas are either reserved or unallocated space.
UNIX Administratosphere 
Very cool, It’s crazy that companies use so much