I found a laser pointer in a drawer, so I looked at all of the arduino laser projects on instructables.com; I may try to build a laser-based sound transmitter thing but for now I’m going to try a morse code sender. If I get crazy, I may try a webcam based decoder; but first the encoder.

Step 1: connect the laser pointer to the arduino. I stuffed one wire into the spring, and wired that to the GND pin. Then I taped the 5V wire to an alligator clip and clipped that to the end of the barrel. Plugged into usb and voila - the arduino is powering the laser.

Step 2. A few google searches later, and I found a handy blog entry with a morse code generator for Arduino. Upload the sketch, change the pin to my pin for the laser, and voila!