Dropbox is a file synching and backup tool that I began using a few months back. It is now one of my favorite tools.
You install a service and designate a folder as your "dropbox" and then register the machine with your online account. You can do this on as many machines as you want. When you add content to the folder, all the registered machines with it installed synch the folder together.
So I have one common "code" folder on my 2 home laptops and work PC that I keep in synch. It also stores the data in a secure web repository and has version control.
Dropbox is useful for synching multiple machines or collaborating with a group of people that have synched dropboxes to the same account. It works over the web on port 80 so you don't have to worry about VPN's or corporate firewalls or anything. It also works on almost all platforms and is free (up to 2GB storage).