The Internet Protocol version 6 is a new version of the Internet Protocol we all came to love over the last 30 years. A big increase in internet capable machines have depleted the total amount of about 4 billion IPv4 addresses. IPv6 has a much larger (in the order of 6*10^27 addresses per square meter of the surface of the earth) address space and speed improvements in the processing of packets. Large scale adoption of this new standard is still some time away, however many governments have mandated IPv6 on government websites and when negotiating new IT contracts.
Heise-online, a large Germany-based technology website, has held their own IPv6-day in September of 2010. The test was such a success, the few problems problems were related to older software, that two weeks later the website was switched to a dual stack setup permanently.
At Kumina we have a dual stack setup at our office since 2008 and a lot of our servers have dual stack connectivity. All our own servers (mail, web, etc) are dual stack and we try to get our customers to run a dual stack setup to be future ready (And most do already) .
The biggest hurdle that must be taken for IPv6 to become widespread is the willingness of consumer ISPs to provide their customers with native IPv6 connections. But we are ready!
Update: Check if your IPv6 is working!