If you use multiple computers, you have to check out DropBox. It hooks into your file-manager (Linux, Windows, Mac) and gives you a special folder that’s synced to all of your machines as well as being accessible via the web (both authenticated and a “Public” folder.) If you’re even mildly interested they have a great demo video on the link above.
If you have your own web hosting, I saw a great tip on the Planet GNOME feed for setting up a URL that’s easier to remember than the one DropBox gives you.
If you’re running Linux, it’s also possible to use DropBox with no file-manager or GUI of any kind. (Also seen on Planet GNOME.)