comcast has ipv6 trials going on now, but only in one or two areas: http://www.comcast6.net/

you can get a free tunnel from a number of providers like http://www.tunnelbroker.net/ or http://www.sixxs.net/

In the UK, Andrews and Arnold (aaisp) offer IPv6 by default for their DSL customers. There aren't m/any consumer routers that support it, but a Vigor 120 ADSL PPPoA to PPPoE bridge can be used in front of a single PC or Linux router.

In Australia, Internode has made IPv6 available to its customers.