I've been using DynDNS ( http://dyndns.com ). They have slightly higher prices than registrars such as GoDaddy, but I trust their brand more and haven't encountered any behavior that looks suspicious. Also, I used to host my websites from home via a cable modem, and their free dynamic IP address services worked very well.

To be honest, I haven't ever considered switching; Has anyone switched to or from DynDNS and have an anecdote about their experience to share?