Let's say you're cheap or you can't afford a fixed IP address and let's say you also want to be able to access your Linux box from the internet but you don't want to have to constantly know the IP address of that box.
Well, if you have your own website (that supports PHP scripting), you can still get around this. Check out this article that I just wrote on how to work around this using some PHP, some Apache mod-rewrite and a simple cronjob.
Maybe you already know of http://www.dyndns.org/ ? Never used it but I’m guessing it should make the whole job easier.