Ask HN: What's on your home server?

It's been years (over a decade?) since I've had a server at home but I'm setting one up for media and I got to thinking: what else should I do with this box? So I was wondering what cool/nerdy/weird stuff you all are using home servers for. DNS and file sharing seem like obvious applications I could set up. I already run email and web on a VPS so that's taken care of. What are you doing with your home server?