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
Amazon Route 53 - Amazon Route 53 is a highly available and scalable DNS web service.
No-IP - Dynamic DNS and Managed DNS Provider
DNS Made Easy - DNS performance, reliability, and security have never been easier.
DNS-O-Matic - DNS-O-Matic (dnsomatic.
GoDaddy DNS - GoDaddy DNS helps manage website performance, reliability and security.
iWantMyName - Register your own custom domain for web applications, email, blog or website such as Google Apps...