I have a DockStar - it works well. It's essentially a tiny computer that can be set up to run OpenWrt or Linux, so if you're so inclined you can set it up as a iTunes server, BitTorrent server, etc in addition to serving as a hard drive host. I'm using the plain-vanilla, out of box software load, and while it works with PogoPlug as the other poster mentioned, it's not necessary to use the PogoPlug software - you can set things up so that each USB drive that you plug into it is accessible via a network share. The device's Amazon review has a good walkthrough on how to do this.
I like the device quite a bit. The box is tiny and uses very little power, and mine has been reliable. I recommend it.