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
Freenom - Provides free website domains using .tk, .ml, .ga, .cf, and .gq.
No-IP - Dynamic DNS and Managed DNS Provider
.co.vu - 3 Free .co.vu Domains for 1 year
DNS-O-Matic - DNS-O-Matic (dnsomatic.
FreeDNS by Afraid.org - Free DNS hosting, lets you fully manage your own domain. Dynamic DNS and Static DNS services available. You may also create hosts off other domains that we host upon the domain owners consent, we have several domains to choose from!
iWantMyName - Register your own custom domain for web applications, email, blog or website such as Google Apps...