I would try ibackup.com, but you probably still have to sign up with these browsers. I think what happens when you share, however, is the files are for any user of the service to download, but not sure of it. I've never found it either, but have been wanting something good, although I don't know if there's control enough that one can upload to another person's directory, or if it's an all or nothing share, read and write.
