For those of us on cable or DSL who are slightly too cheap to pay for a static IP, dynamic DNS services are really useful. My DD-WRT based router knows how to talk to dynamic DNS providers, so setting it up is really easy.
I've tried both DynDNS and No-IP, and while they work quite well they're kind of annoying. They really want me to sign up for a premium service, after all that's how they make money. As a result I need to periodically visit web pages to confirm that I'm using an address or pay a fee. It's not a big fee, but I'm already paying someone, DreamHost to host DNS for me, and they've got an API...
So I threw together a little script that implements the DynDNS API and modifies your own DNS zones using the DreamHost API. You can get it from here: https://github.com/ianloic/dreamhost-ddns
The setup instructions are included in the README. Hopefully they're pretty self-evident, but they are written from the perspective of someone who ran their own DNS servers (primary and secondary) for ten years.