Sean Hodgins created an Arduino-based robot that avoids light by navigating using a neural network:
This project is meant to teach about utilizing neural networks in robotic platforms. There will be a 3 part video series on the Make YouTube channel on building the robot. It will start with prototyping and design, then move onto assembly and testing, and finally programming and running the neural network. You will be able to follow along and make your own robot in the end.