I've also been wondering about that. I saw some old powerbook ads, and they showed that you could access your computer from anywhere in the world remotely, just by being connected to the internet. Can you still do this?
I don't think this is a mac issue. You'll have to set up your home router to foward print requests to the IP of your printer. I think you'll need port forwarding or something.
But it is doable--you would I think add a printer by network address, which would be [yourhomeip]:[yourprinterportnumber]