I can use my own domain for free and it works just fine with IPv4 and IPv6.
I'm using it with am apple airport router and it's working fine
No-IP - Dynamic DNS and Managed DNS Provider
DNS-O-Matic - DNS-O-Matic (dnsomatic.
iWantMyName - Register your own custom domain for web applications, email, blog or website such as Google Apps...
BuddyNS - BuddyNS is the fastest-to-synchronize DNS service on the Internet.
Duck DNS - Free dynamic DNS hosted on Amazon VPC
XName - Free DNS hosting.