Those do look like they'd be fun to build.

I've been thinking about building a big "Jacobs Ladder". That would be fun. Every once in a while, I look on Ebay for a high voltage transformer. One day, I'll have a weak moment and buy one.

If you don't know what a "Jacobs Ladder" is, its what you see in all the old science lab movies. Its where there are two rods spaced close together at the bottom and get farther apart toward the top. Then a spark is introduced at the base and allowed to travel up the rods for that cool mad scientist effect.

The transformers typically go for about $30 - $50. The rest can be made out of spare parts.