At some point you are going to want to sense ambient brightness with better precision than your trusty photoresistor without adding complexity to your project. When that day comes, go get yourself a TEMT6000 ambient light sensor.
The TEMT6000 is supposed to be adapted to the sensitivity of the human eye, but I found it preformed sub-par in low light conditions. It does however work very well reacting to very small changes in a large range of brightnesses. Because it is meant to mimic the human eye, it does not react well to IR or UV light, so just make sure to note that when considering using it in your project.
Supply Voltage: +5VDC 50mA