OK, so I'm a networking geek - but many of you already knew that...
Today is World IPv6 Day, and many prominent websites are opening/premiering their websites to IPv6 traffic today. I decided to play along, and to use my Ubuntu Linux system (a ThinkPad T41p) as the guinea pig. Now, most folks working in the "home IPv6" world use a straightforward IPv6-in-IPv4 tunnel (as described, with a FREE tunneling service, in Dan York's excellent article), but--alas and alack!--my ISP (Windstream) does not yet support tunneling with their DSL modems. Thanks to a reminder from my Twitter friend @sjsawatsky, I rediscovered Teredo, an IPv6/IPv4 technology created by Christian Huitema at Microsoft and codified in RFC 4380. (You KNOW we can't talk about networking protocols without at least one RFC reference!)
In simple terms, a Teredo client uses IPv4 UDP to communicate with a Teredo server, which then pushes the traffic into the IPv6 Internet. If one is lucky enough to have an IPv6-capable ISP, one might run their own Teredo server to handle IPv6 connectivity for an internal (e.g. home) network. Since I'm NOT in that position, I had to rely on the stock Teredo client and a public Teredo server. Thankfully, there's a Teredo port for Linux, and it's available for Ubuntu through the Ubuntu Software Center as "Miredo". The only glitch in the installation was that the Teredo servers listed in default configuration file were either unavailable or swamped, so I switched over to miredo.remlab.net and connected easily to the IPv6 presences of Google, Facebook, and CNN. Now, you may run into some DNS goofiness, since your no-IPv6-here ISP's DNS may not return IPv6 addresses to your queries, but I found that Firefox supports URLs with raw IPv6 addresses in square brackets, like http://[2001:200:dff:fff1:216:3eff:feb1:44d7]/ (If you've done your job right, that last link gives you The Dancing Turtle!)
So, it isn't too late for you to join in on the celebration of World IPv6 Day. Those of you in the Windows world can get what you need from the Microsoft Technet link below, and non-Ubuntu Linux folks can get the Miredo source code from the second link. One word of caution: Either of these techniques gives you a PUBLIC IPv6 address, so make sure that your security is up to snuff. Other than that, enjoy!