Just right for the coming World IPv6 Launch there is an update of the library to connect our Arduinos with the IPv6 world.
It works well with the Arduino Uno board and the Arduino 1.0.1 software. The library was written for ENC28J60 based Ethernet Shields like that from http://www.ekitszone.com - it doesn’t work with the standard Arduino Ethernet Shield.
After uploading an example sketch and plugging in the board it can be “pinged” easily:
There are two examples included: IPv6WebServer and IPv6TelnetServer.
You will find the library with detailed instructions at https://sites.google.com/site/ghoelzl/ipv6ethershield.