I used one of June's pyrex dishes, a 1/4 inch of water and some cooking oil. I put the dish between two chairs and positioned the camera so it was pointing straight down at the surface of the water. I added some of the oil and let it collect into little spheres on the surface of the water.
I learned you don't want to stir the oil/water too much because it will continue to move for a long time and it creates air bubbles on the surface, which are not as interesting as the oil itself.
This was a lot of fun to do. If you want to try it out, here are some suggestions.