Since 17 August, 2011 arnowelzel.de is also accessible via IPv6. For testing purposes you may use http://[2a01:238:4318:a200:1bd7:fae3:bba0:cc2e], but the domain name also works in a “native” IPv6 environment.
Update: There is an AAAA record for the official IPv6 address – therefore don’t use the address above any longer.