[Source: Stay at Home Educator.com]
Oil and water droplet painting is the result of mixing cooking oil and colored water to create a beautiful, slightly marbleized effect.  You can find such paper at a craft or stationary store, or you can invite your kids to help you make some of your own.
Supplies needed are a shallow pan (same size or bigger than the paper), cooking oil, plain water, dyed water (we used liquid food coloring), heavy paper (we used heavy sketching paper, but watercolor paper would be even better), large baking sheets, and eye droppers.
Learn All About this Activity on Stay At Home Educator