Comcast has been for once doing something laudable, and has been
pushing IPv6 deployment throughout their networks, and while it's not
everywhere yet, they (as of the end of last year) had 25% of their
quite substantial customer base enabled for IPv6 use. Hopefully, the
rest of the industry will follow suit and we'll see IPv6 adoption pick
up significant steam, both amongst hosting providers, as well as
consumer ISPs.
Time warner cable is the same. It's available pretty much everywhere on
their cable net.