Cheap NAS for connecting a USB drive to the network

"I like and use FreeNAS as well, but currently we are using an over-kill solution at the office. I took an old computer (therefor free), and set up Ubuntu on it then just share out whatever else I have inside or connected. Way heavier than FreeNAS but here were my reasons.

I could set up every bit of the existing internal disk not needed by Ubuntu as an NTFS partition shared out as NAS but readable in any Windows computer in the future if I had to pull it for some reason.
I like having an Ubuntu box around for general purpose linux use, in case I want to try or test anything.
I'm not using it anyway so why care if it is the most efficient use of the box.
FreeNAS is fast, efficient, ""just worked"" right out the box is highly configurable, and was fine for the geek in me, Ubuntu just seemed a little more user friendly in the end for others who were trying to figure out what was going on as far as mounts and shares."