If you are like me, who has multiple computers with varying amounts of hard disk space, then you definitely will need a way to copy/back-up files from one computer to another over the network.
Personally, I use scp (secure copy or cp over ssh) to transfer files and subdirectories. For convenience, I use Transmit on the Mac to transfer and its Synchronize feature makes it even easier to mirror files.
How about you? What do you use?