Does anybody know of a dynamic DNS client updater software for services like dyndns.org, zoneedit.com and such?

I've googled quite a bit to no avail, but search terms are so generic they return a lot of irrelevant stuff.

My router is working with dyndns, but I'm using zoneedit for my new web server. I'd be glad if I could delegate the task of updating the DNS server to the PowerBook itself (running System 7.0.1) and not having my MBP running 24/7.

Thanks!