If you are interested in reading up on Teredo check out:
As odd as it sounds, Cisco is not doing a lot regarding Teredo. It is mentioned briefly here and there on CCO but if you do an actual search on the CCO website you get back zero results.
Oh, forgot to mention that the Teredo prefix has been assigned from IANA also, it is: 2001:0::/32
It is my understanding that Microsoft will be changing Vista within the next month or so to start using the new range instead of the experimental Microsoft prefix of 3ffe:831f::/32 which is what their existing Teredo server and clients are set up for. currently.