IPv5 and IPv6 sites

IPv4 site

1. http://www.google.com/

2. http://tog.3glab.net/

IPv6 site

1. http://ipv6.google.com/

2. http://ipv6.sunny.ch/

IPv4 and IPv6 sites

1. http://www.ipv6.org/

2. http://www.kame.net/