Volcanoes

Ah yes, the classic science experiment of pouring vinegar over baking soda for a chemical reaction. This is one of my children's favorite activities to do. I have a pie tin set aside to catch the results, and a baby bottle that we use as a volcano.
The volcano was actually a tool that I used to teach my son his colors. I use white vinegar, and pour it into a clear shot glass. We would then talk about our chosen color and add a few drops of food coloring to the vinegar. For green, orange, and purple, and brown, we mixed primary colors. It was the volcano that taught my color the concept of "clear" also.
When I was a child, we made several volcanoes out of salt dough. We molded the dough around a baby-food container or small glass baby bottle, and then baked it in the oven to make it permanent. My brother once made a whole dinosaur landscape which included a volcano. After the baking, he painted the scene with tempera paints. Then my mom helped him hot-glue small plastic trees and shrubbery to the scene.
Whether the simple experiment is a launching pad for discussion of colors, dinosaurs, volcanoes, or chemistry, the baking soda and vinegar reaction is bound to remain a favorite.