Water drops can be suspended on a liquid surface indefinitely by using acoustic vibrations to prevent the surfaces from merging. I used fairly simple parts for this project. The most expensive item is a stereo amplifier, but they are a common find in resale shops for under $10. I found mine for $6. I used an online tone generator to produce the frequencies which can be found here: http://plasticity.szynalski.com/tone-generator.htm
In this video I ran the speaker at 285 Hz and varied the volume to produce the different effects. There is nothing particularly special about 285 Hz, the drops will stay suspended at other frequencies as well. Any dish soap will also work just as well as another to lower surface tension which increases the stability of the drops.
The 4 inch speaker and 90mm petri dish were both purchased online. Often 90mm petri dishes are labeled and sold as 100mm, which are more common to find. The ones I purchased were also being sold as 100mm, but the actual size could be determined by the reviews. Blunt tip syringes were also purchased online to create the drops.
Be aware that this experiment does involve both water and electricity, so there are potential hazards involved. It should not be attempted unless you are familiar with properly dealing with such hazards.
I first learned of this experiment from slow motion footage recorded by Roberto Zenit, National Autonomous University of Mexico. You can check out his footage here.