Hello, I'm working on a small school project now. The task is to send a laser signal from a pointer to a smart car with a receiver. The car will then be affected based on the laser pointer. But I don't know what type of receiver I should use. I have tried a photoresistor, but the resistor is too slow when it is going from HIGH to LOW value. So I'm looking for other options. Any idea anyone? 
Any IR phototransistor or photodiode would work as a replacement for a photoresistor and would be much, much faster in response.
You could also use an IR receiver for remote controls to receive the data. The pen laser should work fine as a replacement for an IR LED. It changes your design a bit but you don't have to worry about problems like filtering out ambient light. A Multi-Protocol Infrared Remote Library for the Arduino