We have 2 computers in our house, and often my wife and I need to share files back and forth or use the same file on different computers. We could mail each other. Or we could use a USB key. Or we could log into the other computer. These work, but they're cumbersome. Dropbox works better.
It's a fairly new file sharing software that I recently installed on both our computers. When I put a file in the dropbox folder on my iMac, it shows up near instantly in the dropbox folder on my wife's PC. And when I edit it on her computer, it gets updated back on my iMac as well. Nothing to it. There's also a web interface, should I need to access these files online or share them with someone else, and version control, should I delete or overwrite a file accidentally.
I like. Give dropbox a try.