Different programs built into the Lego Mindstorms NXT firmware that use the Light Sensor which I use to make "Music" and a "Magic Wand".
Video Soon of music Demonstration.
Step 1: Supplies
All the Supplies you need come prepackaged with any NXT* set you get (Retail, Education, 2.0, etc.)
One NXT Intelligent Brick - I'm using the Firmware that came with my NXT 1.0 around Christmas
One Light Sensor or possibly Color Sensor
Medium or Long NXT Cable
Four 15 Hole length Technic Beams
Various Connectors shown in Image 1
*With the NXT 2.0, I do not know if the Light sensor tests work with the color sensor, You may need to get a light sensor, I am not sure.
Step 2: Build the Shaft/wand [People Doing Only the Required:Skip This Step]
Stick the Various connectors in like Image 1, Then Put the Light Sensor on the two connectors sticking out from the side at the top, and then the NXT brick onto the Bottom two sticking out from the side at the bottom. Attach cable from light sensor to Port 3.
Please note that I messed up with the photos while rebuilding it, if you attach the NXT brick using the studs from Image 1, You will NEED to use a long cable, Image 2 uses a Medium cable.
Step 3: Accessing the Programs on the NXT Brick
Music: Turn on your NXT Brick, and scroll left to "Try Me". Click this, and scroll to "Try-Light" Click this, and follow the on screen instructions.
Magic Wand:Turn on your NXT Brick, scroll to "View" and click it. scroll right to "Reflected Light" and click it. Scroll to "Port 3", and get ready to say your magic spell *coughexpelliarmouscough* and click it as you say it, then hit the small grey button after a second or two (or at your leisure)
I know this is pretty stupid but you wouldn't beleive how many people don't even know about the different View/Try me stuff that's on their NXT Brick.