It's not free, but it's only like $3/mo. You get 1 month free, and with every referral you get a free month. It's by far the best and easiest dns service out there. It was a side project of an HN'er as well. He did a fantastic job with the service.
Makes DNS easy. When I wanted to set up google account stuff (mail, notes, docs, etc). I just clicked on the domain edit, clicked edit (or something along that verbiage) and chose it from the list. Also used that to set up my A record pointing my personal domain to my username.github.com site.
http://1984hosting.com will take you to their English site (although the What is FreeDNS? page is in Icelandic).
Not ideal, but not terrible either.