We’ve covered plasma speakers before, and these vids don’t really add much in the way of additional info, they’re just different variations on the theme — a theme I find endlessly fascinating. The top vid is by way of TechEBlog, the second is from John Warren (via Adafuit). Check out his blog post below for more details on his set-up.
Update: Here’s the Instructable for the first speaker rig shown above. Thanks to reader David S for pointing us towards this.