Exploratorium
Exploratorium: Science Snacks: Klutz Proof Density Column
An activity to help you create a density column that contains layers of liquids that are separated by different densities.
Other
Lapeer County Schools Science Resources: Density Lab
A simple lab experiment for students to find the density of two solids and a liquid (does not use water displacement). Note that number 1d should not state "weighs" since mass is being found.
Treehut
Suzy's World: How Come Some Liquids Don?t Mix?
This site from Suzy's World explores how and why certain liquids mix better than others. Content includes fun facts and a classroom experiment. This site also includes links to additional information on related subjects.