A plasma globe is a must-have item for any aspiring weekend physicist. A variety of interesting demos are possible using the swarming streams of ionized particles produced by conducting a high voltage spark through a partial vacuum. There are many informative web sites about plasma physics (see sample links below), so this instructable just provides construction details w/o the science.
The most challenging step when building a plasma globe is the evacuation of a glass container on the cheap -- vacuum pumps can be pricey. However, a good quality glass jar w/a narrow neck, a rubber sink stopper, a threaded bolt, a suitable high voltage power source (such as a Tesla Coil), tap water, some hardware and epoxy as well as access to a freezer are what you will need to assemble this simple project. If you can boil water, this project will be will be a breeze. :>D
Of course, use common sense and always keep safety in mind while operating the globe. This project involves electricity and water!
If you accidentally connect with the high voltage circuit, the resulting shock can really ruin your weekend plans. For Further Infohttp://powerlabs.org/http://www.pppl.gov/