Wuala is an interesting 'social storage' solution, see http://www.wuala.com
. It's interesting because you can earn free storage space through trading of your own storage. And your quota goes up when your computer remains online, perfect for a low power plug computer ...
Technically, it's not that difficult, wuala comes as a java application. Unfortunately, I have not got it running with the normal OpenJDK, but with the specific ARM headless version of Sun the wuala software runs happily. Though it 's unclear what version I will have to use finally. The Sun ARM package is a 90 days trial, is not free for commcercial packaging (OK) but what about a single home user ?
The only drawback of the plug with Wuala is that not all capabilities of Wuala are exposed in the command line interface, so for the moment there is no method to setup automatic backup (at least I have not found one yet). The solution would be to run a full java (with UI), but there is no such bundle (yet) for ARM.
I'm running a Debian version on my plug see http://crichton.homelinux.org/~marc/eib_sheeva.html
for the specific version (and how to install it).