Here are a collection of interesting sites to visit on World IPv6 Day
The World IPv6 Day "Eye Chart" causes your browser to visit a number of prominent IPv6 Capable sites:
IPv6 Day Survey - test of dozens of IPv6 capable sites for differemt protocols (HTTP, SMTP, XMPP, etc)
Akamai Real Time Statistics:
World IPv6 Day participant site status:
RIPE Network Information Center Dashboard, including AAAA record visibility:
Path MTU analysis and research:
Feel free to tell us about more in the comments!!