Some services I have liked in the past are:

• Syncthing if you have some storage space
• A backup server
• Websites and Demos
• i2pd and your own i2p website/blog
• Monero mainnet and Haveno
• Crypto Mining to support the network not to make money (Limited to a small portion of your resources)
• Game Servers
• VNC on some virtual machines for a networked device
• A remote containerized development environment

But there are all kinds of things you can do with some continuous computation and networking!

I was going to say I grew sugar beets for yeast culture and ethanol production as well as canola for lubricants and green diesel. Every climate has something you can grow for fuel and machinery lubricant. Yeilds will obviously vary depending on experience, land, climate, etc. some good resources are JTF Biofuel Library and Energy.gov

It’s also worth noting Syngas production in some sort of gasifier with almost anything is a super easy way to produce fuel too.