Here is what you will need:1 laser
Any old laser will do red, green, blue, anything within your visual spectrum is just great. The only thing I'd suggest you avoid is using a strong laser. If you're into laser you'll know the ones I mean: the dvd burner, blue-ray, I can cut through duct tape ones. Since you'll be bouncing laser beams off all over the place, I'd urge you to not exceed 50mW and at the very least use some sunglasses for basic protection.
Here's the one I'm currently using: http://www.dealextreme.com/details.dx/sku.100961 mirror
Size doesn't matter, it's how you use it. :) No wait! Erase that! Get something small enough to handle with ease.1 small puck-shaped neodymium magnet
The one I used came with the Arduino sensor pack 900.1 small metallic strip
or anything that you can use to move the magnet without moving the mirror.some water
Distilled preferred, but not required.
something to elevate the mirror only slightly above the height of the magnet
[optional] a squid type third hand
It's a priceless tool and if you hadn't built one for your workshop I encourage you try. The most excellent instructable on how to do this is here: http://www.instructables.com/id/Third-Hand-A-multi-use-helping-hand-for-electro/