Cloud services are all the hype. It sure is nice to have all sorts of stuff available anywhere, anytime. But, do you actually want to trust all your data to some external provider? NSA scandal aside, you cannot know for sure what some provider does with your data, and you could get left out cold should that provider cease operating for any reason, or if you stupidly should get locked out of your account. There comes in the private cloud, i.e. all the same stuff, but self-hosted. Of course, you'll have to see about backups on your own, as well as make sure your stuff is available as you need it.

OwnCloud is a free (as in FOSS + beer) such cloud server. It started out for basic file storage, but a lot of additional features have been added since then. As of 2013-12-30, version 6 is current. The Debian package for the Raspberry Pi being stuck at version 4.0.4, that one is not the way to go.

Note: c't doc on OwnCloud: http://www.heise.de/ct/artikel/Alles-auf-Abruf-1908923.html