If I recall correctly, when I had the Power Mac 7x00, we had to buy some kind of serial cable to connect two Mac together. The hard drive of one mac could be shared with another Mac using this method. We accessed the internet via phone line.
Given that we have relatively fast wifi connection at home now, what do people use these days to access the hard drive of another computer regardless of the OS? I am looking for something like a home version of dropbox without access to the cloud due to privacy.