Here is a seriously off the wall but fun project: How to develop .Net Core applications to run on a PocketBeagle. I think the PocketBeagle is the smallest system that can run .Net Core (at least among boards that are commonly available).
http://git.munts.com/arm-linux-mcu/doc/AppNote11-PocketBeagle-Gadget.pdf
http://git.munts.com/arm-linux-mcu/doc/AppNote12-Flash-LED-C%23-Core.pdf
http://git.munts.com/libsimpleio