Google Drive Free Storage
Get an extra 2GB of Storage with Google Drive, head to google and secure your account. See Gizmodo.com here for details, they did a similar offering last year, the process is only a couple of clicks.
Copy.com
Recently Copy.com announced it was discontinuing its free storage service (see press release here) so users of this service, will probably shift to Google Drive, Dropbox, Box, Microsoft OneDrive, or iCloud, for personal storage online using their free services.
Ubuntu.one
One of the early such service Ubuntu One (and it did have versions for other operating systems), closed down the year before last, so the variety of free storage has reduced.