This week I started several weeks of labs on dating methods in my undergraduate archaeometry class. For tree-ring dating, I like using the skeleton-plotting exercise from the University of Arizona Tree-Ring Research Laboratory's web pages. You can start with a good overview of the method, and then go on to Try Skeleton Plotting for Yourself! You get a cool Java applet which generates a tree-ring "sample" for you to work with, a master chronology to match against, and the chance to peek at the Answer. You can make your life tough if you want to by including missing or double rings.
Try it for yourself. What do you think? Do you know of other useful online resources, especially applets, for teaching archaeometry?