With the tragic events leading up to the large oil spill in the Gulf of Mexico, I felt it was important to teach my children what is so terrible about the situation.
Oil experiments really get the point across easily to younger children. Pour a cup of oil in a small bowl and add a few drops of food coloring. Then pour colored oil into a big bowl of water. The children can place a few toys (or if you really want to proove a point use a small stuffed animal) in and see how difficult it is to get the oil off. You can also experiment with different means of getting the oil out of the water!
Here are some of the resources I've used:
Big list of resources - Earth Scouts
Oil & Pain Contamination Activity
Effects of Oil Spills on Birds
Oil, Oil Everywhere - a book on the Exxon Valdeze with worksheets and lesson plans
Fossil Fuels, Facing the Issues
Impact of Oil Spills on Our Oceans