Ubuntu One is your personal cloud. You can use it to back up, store, sync and share your data with other Ubuntu One users.
Ubuntu One gives all features and 2 GB of essential storage to everyone.
Features available: https://one.ubuntu.com/features/ [5]
Compare the (2) plans: https://one.ubuntu.com/plans/ [6]
Check out Ubuntu 9.10 Server Edition: Cloud computing made real: http://www.ubuntu.com/news/ubuntu-910-server-edition [7]
Links:
[1] http://pulse.veltsos.com/category/it/cloud
[2] http://pulse.veltsos.com/category/it/software/software/os/linux
[3] http://pulse.veltsos.com/category/it/open-source-foss
[4] http://linux.philosweb.com/drupal/files/1ubuntu_sync-share-promo_2.png
[5] https://one.ubuntu.com/features/
[6] https://one.ubuntu.com/plans/
[7] http://www.ubuntu.com/news/ubuntu-910-server-edition