Be aware that http://www.whatismyipadress.com may not work. In my case, that page does not show me my IP adress but instead shows the IP adress of one of my ISP proxys that manages the traffic. After you get the IP adress from that page, do a "nslookup IP_adress" to check the domain name.

If you have an dynamic IP adress there are still ways of accessing your home computer without the need of knowing your IP adress every time.

One way of doing this is with a Dynamic DNS Update Client. For more info check out http://no-ip.org . They will redirect something like vendicate.no-ip.org to your IP adress. When your IP adress changes, the Dynamic DNS Update Client sends the new IP adress to them. So, you just have to remember the domain name. So if you have a web server on your box instead of going to http://IP_adress you would go to http://vendicate.no-ip.org. The same goes for a ssh server, which I recomand if you want to access your box from other places. Preaty neat.