Thanks to the rapid adoption and speed of internet, we now live in an era where we put much of our data on the "cloud". Of course it's not the real cloud in the sky, but it means that more and more digital data nowadays are placed on web servers around the world. This trend is growing rapidly because we find it practical, highly accesible, and more secure than traditional storage system on hard disks or local servers.
Ubuntu, the Linux-based operating system, is also offering its users and others a free storage, called "Ubuntu One" cloud storage service, a service similar to Dropbox, iCloud, Google Drive, Microsoft SkyDrive, but in my opinion, is more trusted than others I mentioned, since it comes from the free open-source environment :).
Every basic free account of Ubuntu One users will get 5 GB storage space for free.
Today, Ubuntu One has announced an exiting promotion, offering every users to get even more free storage, up to 20 GB (so total free space will become 25 GB), by inviting friends or family or anybody to sign up for a new Ubuntu One account using a unique referral link.
For every succesfull sign up of new Ubuntu One account you invited using your unique referral link, both you and the signee will get additional 500 MB of free storage. With maximum of 40 people signing up via your invitation, you will get 20 GB additional free storage, besides the 5 GB free space when you signed up for Ubuntu One account.
So, if you want this free cloud storage from Ubuntu One, just go to Ubuntu One website (yes, that's my referral link :) ), complete the sign up process, and then go to Ubuntu One Dashboard for your unique referral link.
Then you can invite your friends, family, or anubody to sign up for Ubuntu One account via your own referral link for additional free storage for both you and your friends.
Note that the Ubuntu One service is not only available for Ubuntu OS users, but also for Windows, iOS, Android, and other OS users as well, or anybody with internet access. Ubuntu OS comes with Ubuntu One application pre-installed on their system, but other OS users can also join this service and installing its application client on their OS or access it via its online website or mobile application.