Go ahead and ask your students on the first day of class what economics is all about and I bet most of them will say, "Money." Be ready for their looks of despair when you tell them economics is actually all about scarcity and how to deal with the fact that everyone wants an unlimited amount of scarce resources.
Anyway, money is exciting to students as each one of them is going to have tons of it when they get older (at least that is what they always say) and it allows them to purchase the latest and greatest things out there on the market.
When you get around to talking about money..."Explain the role of money as a medium of exchange and how if facilitates exchange", be sure to share this site with your students. The Bureau of Engraving and Printing does a clutch job showing all of the cool safety features of our paper currency. I always found that my students were very interested in learning more about money after seeing the cool watermarks and security threads that are found in our paper currency. They also were surprised to learn that the Secret Service was in charge of combating the counterfeiting of US dollars.