After some thought and research, I found that Numato have GPIO boards which work with PC's. You plug their GPIO USB device into your PC and then can control the pins from your choice of many different languages (you need to use an API which can write to a serial bus).
I'm excited by PC based GPIO programming because:
- The project I'm thinking of working on does not require a tiny portable computer.
- I get to work in Visual Studio in a Windows environment, which is what I'm used to.
- While Raspberry Pi and Arduino are not expensive, the $20 USB device is cheaper :)