finger, nslookup, ping, traceroute, whois: UK IPv6 Resource Centre / The test page
ping, traceroute, tracepath, 6bone registry, DNS: JOIN / Testtools (German language only, but should be no problem for non German speakers)
traceroute6, whois: IPng.nl
AAAA Lookup Checker http://www.cnri.dit.ie/cgi-bin/check_aaaa.pl