I use http://www.no-ip.com

Their free domain names are corny, but hey, it works! All you have to do is sign up, then install an agent on the PC you want to connect to.
Assign your pc a static address outside of your DHCP pool, or reserve one in your DHCP pool.
As soon as you figure our which ports you need to open, then you will need to configure "port forwarding" within your router to point to your pc that you want to access.
It's a pretty simple setup. Good luck!