I went from a desktop to a laptop so I needed somewhere to put my drives will all my data. I built this as a Linux server for simple file serving. Then decided to tinker with it and created some virtual machines with VirtualBox type II hypervisor to test LAMP, media server, HTPC, play with a email client,etc. It went very well so after a year I went full on with a type I hypervisor. I used ESXI and I'm really happy with it.
After couple of years running ESXI I don't have as much time to play with it so thinking of doing a simple update, run FreeNAS or similar and leave it as NAS only.
PS. The pictures are of the first "case" I built for it. I didn't have much money for it and couldn't find a case without huge amounts of space wasted so I built this. It was meant to live under the sofa so had to be small. Didn't save much money (you can get a case for next to nothing) but I do really enjoy a weekend DIY project and it came out pretty space efficient. After a while when I got more drives I bought the Fractal case.
EDIT: Somebody asked to list the parts for the DYI case, so here it is. Bare in mind I built this years ago so it might not be totally acurate. It should however give an idea:
-Aluminum Profiles: http://www.homedepot.com/p/Fasade-4-ft-Large-Profile-Outside-Corner-Trim-in-Brushed-Aluminum-178-08/203232532 I also used a flat one for the drives cage and mobo but can't seem to find it.
-Tin sheet: http://www.homedepot.com/p/MD-Building-Products-36-in-x-36-in-Plain-Aluminum-Sheet-in-Silver-57000/100351161 Im unsure about this one, I remember it cheaper. it was thin enough to be cut with strong scisors. But gives an idea.
-Bunch of nuts for the threaded rods, end nuts for the top and bottom of the rods. Whasers, screws and nuts for the mobo and secure the HDD cage. PSU and HDD were secured using regular case hardware I believe.