+1 for freedns.afraid.org ... you can use one of the existing/open entries, you can put up your own domain for yours and others' use (did this for bbs.io, though I nuke entries that aren't bbs related), or you can pay for private use of your own domain. Works great overall.
DuckDNS[0] is another alternative that I've been seeing posted on reddit. Works exactly like the rest -- curl a URL to update your IP. Really nice staff. I've got a PR[1] for a homebrew formula for duckdns which uses launchd rather than cron (which has been deprecated since OSX 10.8).
I switched from DynDNS to NoIP last year, but I'm probably going to switch again soon; NoIP's Mac auto-updater is broken and they don't seem to give a shit about fixing it.
I use https://freedns.afraid.org/. I appreciate that they support a URL that you can cURL, but I've never actually needed that, as Comcast never changes my IP address (although they're allowed to do so, I've had the same address for at least 3 years). Personally, I just use a subdomain on one of the domains they manage, and use a CNAME on my own domain to point to that.
Another +1 for freedns.afraid.org. I used them for years on my home FreeBSD gateway serving my domain on a dynamic IP, and didn't once have an issue. I think I only emailed the owner once or twice about some small matter, but he responded both times politely and quickly. For a free service, pretty impressive. Highly worth supplying a donation I would say if you use it.
- https://freedns.afraid.org/
- https://ydns.eu/
What I like about these two is that you are able to update the IP by just curl'ing a certain URL, which works great in combination with a cronjob.
Edit: It looks like OP submitted the tracking URL from the newsletter, his ID is probably going to stick out in their analytics.