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.