Dropbox
Dropbox is a Cloud based file synchronization service that will keep a folder on your desktop (or desktops) in sync with the website. The service all works seamlessly, as long as you have the program running in your system tray.
It allows you to backup 2GB worth of data while under the free plan, and has various paid options to meet the needs of larger file limits. 2GB is definitely enough for documents and possibly a small amount of music.
It also works on Windows, Linux or Mac OS operating systems so it is something that can be utilized by anyone. This is something I would like to see a mobile platform created, for Blackberry or Android to be able to have access to those files anywhere.
To start using Dropbox visit: http://www.getdropbox.com/