Nixie Plasma Ball
In theory it is very easy to make one, if you have access to low presure neon pumping facilities, custom made glass and a tesla coil. The scientifically more correct explanation of how the plasma ball works can be found here. The father of the whole plasma ball is Nikola Tesla. So treat it with respect.
Now. To avoid buying thousands worth of gas pumping equipment and a glass manufacturer I decided to look for alternative sources of low presure gas filled glass items. And guess what! A nixie tube! The basic principle of the nixie tube is an inert gas discharge, where the gas becomes conductive at low presures and high voltages and even glows! That's why nixies work and have that beautiful warm glow surrounding them.
[Source] Hack-A-Day via David “daqq” Gustafik Homepage