Useful Links

IPv6 Information

Google's IPv6 adoption graph

IPv6 usage by country

IPv6 support for important networking applications

Mark Prior's comprehensive IPv6 usage survey

Geoff Huston's IPv4 depletion projections

The IPv6 Timeline from IPv6 Forum Downunder.

IPv4 Information

The Gallery of IPv4 Heatmaps shows similar maps for BGP, open DNS resolvers, RIR Whois, etc.

See Randall Munroe's hand-drawn map of IPv4 Internet address blocks from xkcd #195 that sparked the above research.

Use the map-o-net to find your own location in the structure of IPv4 address space.