This blog post has grown to large. Please refer to the more detailed posts on IPv6 tagged with ipv6:
DNS entries for IPv6 ready web sites
Arecord: normal domain to ip address resolution
MXrecord: email server lookup, must resolve to a server address that is resolved to an IP via an A record
TXTrecord: can be used for an [http://www.openspf.org/ SPF entry]
AAAArecord: Returns a 128-bit IPv6 address, most commonly used to map hostnames to an IP address of the host.
To look up IPv6 DNS entries manually you can use