RetroPie is an emulator suite for the Raspberry Pi. This project was not very difficult, but requited a bit of custumization.
The Pi is enclosed in a lego case I built with the kids. It runs the Raspbian-based image which boots straight into EmulationStation, a console style frontend for various emulators. We use our wireless Xbox 360 controllers for input. And the kids made a custom splash screen, too!
Now I can replay all my childhood Nintendo and Sega classics. With my own kids, which just blows my mind. Full circle.