The 6bone is analogous to the
MBONE. It is a collection of machines doing
IPv6 tunnelling over
IPv4. As
top-level routers start routing IPv6 packets, the plan is that these machines will eventually start doing plain IPv6.
The 6bone is mainly experimental at the moment. See http://www.6bone.net/ for assorted information, including how to join.
And you thought this writeup was going to involve perversion. Shame on you!