Some of you are fortunate enough to have a Microlab in the classroom, here is a introductory excercise to get the inquiring minds working, if not, modify it to your needs.
Other fun activities:
Coffee Chemistry lab (thanks to Mr. Talafuse and Mr. Beals)
Link to Nathan Talafuse's website for the Coffee Chemistry lab. sites.google.com/a/billingsschools.org/talafuse/chemistry-of-coffee