Mozy automatically backs up files and folders you choose, at times you would like it to--such as when you are not using your computer. It is fairly easy to set it up for the first time, as it automatically selects the My Documents, My Music folder, and others for backup, but you have to navigate a Windows Explorer-like file tree to choose other files and folders you want backed up.
Then the wait begins. Mozy moves your files to a safe location--but very slowly. Sometimes the process fails altogether. You can pay nothing to back up 2 GB, or $5 a month for unlimited space.