I have been pretty busy lately with some other projects which I will post later but I did find this very simple project for the Arduino on the Adafruit website. It uses a photoresistor and a piezo buzzer and a very short piece of code. It is easy to build and easy to modify. If you are new to electronics it is a great way to see these components in action.
The blog post has a simple diagram showing all the parts required along with the code.