Most hosting providers and domain sellers will provide this for free. CloudFlare also offers free DNS (which you can use with a patched version of ddclient). C

Most hosting providers and domain sellers will provide this for free. CloudFlare also offers free DNS (which you can use with a patched version of ddclient). CloudFlare uses anycast, so it's fast, and as a DoS protection company, they tend to be more reliable than many of the other free options.