Acoustical levitation is fascinating. Project two banks of directed soundwaves towards each other, carefully aimed so that they create a standing wave node, and into that node, you can deposit liquid or lightweight objects (foam, lint) and they will remain in this area until disturbed. Levitation. Cool!
In this Physics Girl video, Dianna puts together an acoustic levitator kit, the first time that this sort of sophisticated acoustical technology has been available to consumers. Diana even travels to the University of Bristol in the UK to talk with the designer of the kit and to learn more about the physics of acoustical levitation.
You can see the Instructable that details the kit and its assembly here. The kit costs US$70 and it took Dianna and two of her high-domed friends three hours to put it together.