Once you sign up, which takes less than 10 minutes, you can setup the service to a domain name you like, and which you can remember. This domain name will then be associated with your home IP address.
When you are out and about, you can type this address into any number of Internet programs, depending on what you have setup on your network. Eg. If you want to use remote desktop on your home PC, you would type in the domain name into your remote desktop client. DynDNS will forward you through.
What makes DynDNS particularly useful, is that if your home IP changes, either a desktop update client or your router will tell the DynDNS servers update your IP on their records. Many routers have the option to enter in some dynamic DNS settings. You will never have to remember your home IP address again.
If you are connecting to through a router, you will need to setup port forwarding, so that your router will know which computer it should send you to for any of the services you want to use. Check this link for an extended list of ports.
DynDNS opens up a whole bunch of of doors for you. You can setup your home computer as a web or FTP server and connect to them easily. I love this service.
Create your account for free at dyndns.com. They have been around for a long time, but they can never be over promoted.