What is a good specimen to observe in the Compound Light Microscope?

Drop from warm long-standing fresh-water puddle especially if there macroorganisms such as tadpoles, waterbeetles and algae are present. Rich protoozoan fauna can bne seen - amoeba, paramecium, microscopic algae, etc. You can break organisms into groups and then, count number of each organism in group and recalculate to a certain water volume.