I agree with Emerald. I've been testing out quite a few different providers since DynDNS decided to stop doing the free account. No-IP.com is pretty good. They've got a really well developed system thats pretty simple. Not surprising considering that they also do 'pay-for' services. The difference is that they DO still have free accounts.
In case anyone is dead set on using DynDNS (or is forced to due to pre-programmed firmwares using it), you CAN actually still get a free DynDNS account. I found that D-Link actually has a deal with them to still offer a single free hostname. Check out my findings here: http://boomshadow.net/tech/how-to-still-get-a-free-dyndns-account/