Several people have suggested I (re)post information about test-ipv6.com
here.
http://test-ipv6.com ..
tests ipv4 and ipv6 by dns name
tests dual stack (will the client break on World IPv6 Day?)
tests ipv6 by IP literal (teredo can pass this)
gives advice to end user about current status and (depending on
circumstances) more information
"broken" users (can't connect to dual stack) are solicited for info
Caution: does depend on javascript.
http://test-ipv6.com/simple_test.html
Eyeball test only for user, with instructions; no javascript required.
Please direct any comments, flames, etc directly to me instead of the
list. I've added enough noise already :-)