I searched for a free on-line hard disk and I found http://mydrive.ch.
- You get 2GB disk space
- You can upload files via your web browser or you install a network hard drive on your local computer.
- You can install a guest access and pick single folders, which should be visible for the guest.
I use the on-line hard disk for backups and listening to my music, from everywhere I want.
Attention: I wouldn't make MP3 files visible for the guest.