If you have multiple computers and like to keep copies of the same files on all of them, you simply have to try out DropBox.com. It's an amazing free service that lets you keep multiple machines in sync seamlessly.
When traveling, I used to move files back and forth to my laptop using a USB key or copying files by hand. Dropbox creates a special folder on your machine called "Dropbox." Anything you put in that folder gets magically synchronized to Dropbox's servers, and then downloaded to your other machines automatically. Plus, Dropbox keeps the last few versions of each file so you can go back in time if something happens to the current file version. Plus, it is cross-platform and even works on smartphones.
It's totally changed my life. Try it out. If you use my affiliate code by using this link, you'll get an extra 250Mb of DropBox storage for free: http://www.steverrobbins.com/r/dropboxlink. Give it a shot; it's awesome!