• WorldXChange may offer IPv6.
• Unleash offers IPv6 on fibre/wireless circuits, colocation and virtual servers.
• Verizon Business (formerly UUNet) offers native IPv6 connectivity worldwide.

See SixXS FAQ: Where can I get native IPv6 / Which ISP's provide IPv6? for a list of providers worldwide.

• Gogo6 ofer IPv6 in IPv4 tunnels using TSP 1).
• Hurricane Electric offer IPv6 in IPv4 tunnels 2).
• SixXS offer IPv6 in IPv4 tunnels (static + heartbeat for dynamic and AYIYA for dynamic+behind-NAT) through a PoP provided by ACS Data in Wellington, New Zealand.

See also Wikipedia: List of IPv6 tunnel brokers for other options.

If your ISP does not offer native IPv6 transit, and you want to use a 6to4 tunnel to connect to the IPv6 Internet, then you can if your ISP has deployed a 6to4 Anycast gateway. You can test if your ISP does by doing a traceroute to the magic IPv4 address of 192.88.99.1. If your ISP provides this service then the traceroute should stop inside your ISP. If the ISP does not provide the service then the traceroute will either fail, or go to some far away land which will give you poor IPv6 results.

• Clear.net [and Paradise who is owned by Clear.net], http://www.clear.net.nz/
• Unleash announces 192.88.99.0/24 on the APE as of 2 Sep 2008.