Yes, a raspberry pi with a usb drive running samba and minidlna.
I started with an old nslu2, the pi on my network is slug5, as its the fifth machine that has done this job over about 15 years or so.
VLC installed on the chromecast works well with the little remote control, so local media is no harder than netflix or prime.
Edit: the original streamer I used was a Neuston mc-500, which could access network files. The nslu2 was a little slow, but 15 years ago media files were much smaller too. You could record digital tv with a usb dongle and play it back on the neuston which amazed me at the time.
Edit2: the kids had hacked PS2s in their bedrooms that had media players on them that pulled data from the nslu2 as well. It was cool, cheap and worked well.
