I turned a Raspberry Pi into a home media server for my TV
It was really easy to do, too.

One great way to put a spare SBC to good use is to make it a server of some kind. After all, they're really good at staying online for long periods of time, and they use barely any electricity, so they made a negligible impact on your bill. So, why not keep those boards out of the spare parts drawer and make them earn their keep?