I'm currently mounting two rPi boards to two external hard drives. I'll leave one at home and one at work and run BitTorrent Sync on them to create my own little distributed / decentralized Dropbox. Would a blog post when I'm done be interesting?
Short version: BTSync is awesome, ownCloud makes the Pi struggle pretty hard
In this blog post it sounds like I'll be writing, I'll report on sync speeds using 3 nodes and things like that.