The QTR-1A reflectance sensor carries a single infrared LED and phototransistor pair in an inexpensive, tiny 0.5" x 0.3" module that can be mounted almost anywhere and is great for edge detection and line following applications. This sensor is sold in packs of two units.
Every laser needs a holder!
This is the basic laser card module with circuitry built in so that it can be turned on/off with a TTL signal.
A nice, compact 5mW green laser. Fun, but don't point in anyone's eyes.