Marvell is developing awesomely cheap network attached storage and home cloud computing terminals called Pogoplug and Sheevaplug. Those are most often $99 or cheaper, based on open source hardware designs, manufactured by several manufacturers, they are probably the cheapest most cost effective ARM Powered NAS and media streamer home cloud computing solutions. You can buy one of those, plug them to your electricity, connect them to the web using ethernet or WiFi and run some Linux software on it from an SD card and access and do stuff such as hosting and media streaming with the files on a USB hard drive or flash drive.
Amahi is now releasing an open source software, with components from Fedora for ARM and a bunch of other stuff. It can run free software such as web-chess, gallery, wikis, blogging software, groupware that can be installed in a one-click install process. You might not really be able to do this kind of easy one-click Applications marketplace thing using some of the more expensive NAS devices on the market by companies like Synology, Qnap and Netgear.