Today is World IPV6 Day.
Google and Facebook are amongst a group of companies that will offer their services over IPv6. Described as a Test Flight Day, the objective is to help ensure a successful transition as IPv4 addresses run out.
Google has a blog post about the event here.
You can test for IPv6 here.
My readiness score for IPv6 on one of my networks is 0/10. Uh oh.