Hello,
 
To setup a computer with IPv6 public address over any IPv4 connection (3G, ADSL, dial-up, etc. and even behind nested NATs) for World IPv6 Day testing then I suggest downloading the Freenet6 client and running it with default settings; it’s the closest you can get to plug and play IPv6.
 
Freenet6 have the TSP protocol IPv6 server in Amsterdam, so response times should be acceptable.
 
Only the Windows XP/Vista/7 versions have an intuitive graphical interface, while OS X, BSD and Linux are command line only so far.
 
Register and download the client from http://gogonet.gogo6.com/page/freenet6-ipv6-services 
 
Its working very well at my end today, with standard pings to Facebook, Bing, Yahoo and Google defaulting to IPv6 addresses and responses when connected to Freenet6.
 
Regards,
-Ahmed