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
DirectUpdate - DirectUpdate is a dynamic DNS updater with many features.
No-IP - Dynamic DNS and Managed DNS Provider
Marcs Updater - Your router doesn't support DynDNS, OpenDNS or DNS-O-Matic by default or is limited in number...
DNS-O-Matic - DNS-O-Matic (dnsomatic.
OpenDNS Updater - OpenDNS recommends that you use our client-side software to keep your dynamic IP updated for your...
iWantMyName - Register your own custom domain for web applications, email, blog or website such as Google Apps...