Creating a homebrew USB device to get radio signal data onto a network.
The CAN bus is a cheap, robust and simplistic interface between microcontrollers wired together. Here are some low-cost alternatives to CAN bus sniffing.
A quick example of using FFI in Ruby to wrap HID API to talk to a USB HID device in Windows.
There are great resources for electronics beginners to learn Arduino—not for people who want to learn general microcontrollers.
HIDSharp is a great little library for USB HID communication in .NET.
I needed to interface my computer to an embedded device, and I found a way to configure a relatively cheap USB UART bridge to support it.