Everyone is talking about this today. I remember first read about a free nitrogen laser in the Scientific American Experimenters Handbook when I was a teenager. I was more into building a Van de Graff machine but I could still appreciate a laser that didn’t need any complex lasing fluids or expensive tubes or one of those ultra cool multi Joule flash lamps. Ahh.. Such day dreams those made up… Oh yeah, about the laser. Pretty much is uses a great whopping spark to excite the nitrogen atoms in the air to a higher state and in turn that liberates ultraviolet radiation. Cool, eh? Hubert’s page has all sorts of cracking info on how that darn thing works, the kid did his homework Looks like you could build one for less than $50 easy. The 10KV power supply could be obtained from a TV or you might even be able to get away with using one of those cheesy air ionizers you find in second hand shops. Or you could buy one from Information Unlimited. (Weird, I Googled ‘high voltage power supply’ and saw the link, I had no idea those guys were still around! Very cool!)
Hubert’s laser page: Air laser
And if that don’t do it for ya, check this one out you laser pervs! Home built nitrogen (N2) laser
Fear the robot uprising? The robot insects are among us already! 
What do you get when you add air to your LEGOs? No, not crispy LEGOS that don’t go soggy in milk, you get power! This site has all sorts of methods of building motors, valves, and switches that run off from pressurized air and all are made with that classic building material, LEGO. YOu know, it’s not too late to 
for Christmas if you want to mess with them. 
Ouch! The effect of this device is to make it feel like your being melted.