Vaccines are pretty amazing when you think about it. Take a deadly substance and make something that will protect us from the deadly substance.
My wife is a Biology teacher and was teaching her students about Vaccines and Diseases and shared this site with me.
How Vaccines are Made is part of an interactive site, The History of Vaccines, that uses multimedia to explain how vaccines are made, how they work, types of vaccines, and much more. There are also sections on the Scientific Method, Diseases, and Immunity.
The site is very well designed and easy to understand. There is an Educator page with lesson plans to use with the activities also. This is an interesting topic that gets students engaged and interested in science.