tetaneutral.net is participating in World IPv6 Launch on 6 June 2012 :
All tetaneutral.net users get an IPv6 /56 subnet in addition to their IPv4 address.
To enable IPv6 on your debian machine please edit the configuration file /etc/network/interfaces and add the following:
iface eth0 inet6 static pre-up echo 0 > /proc/sys/net/ipv6/conf/$IFACE/accept_ra pre-up echo 0 > /proc/sys/net/ipv6/conf/$IFACE/autoconf address 2a01:6600:8081:XX00::1 netmask 56 gateway fe80::31
Replacing XX with the number attributed by tetaneutral.net team.
More information about IPv6 for tetaneutral.net users here: IPv6 including how to tunnel a /64 in another place where your don't have IPv6 and other cool tricks like managing your reverse DNS for IPv6.
NAT64DNS64 contains information on running an IPv6 only lan with NAT64 and DNS64.