I don't know if this qualifies as hand-on, but in my non-majors college student course I teach trophic levels quantitatively ... we do this so that we can understand the difficulty of figuring out whether trophic levels are indeed declining in various large marine ecosystems and globally.
As I introduce the basics of pyramids of #, biomass, and energy, I also ask them to fill out a very small questionnaire about their diets. I somewhat arbitrarily assign a trophic value of 2.0 for strict vegans, 2.2 for lacto-ovo-vegetarians, 2.4 for omnivores, and 2.6 for students who consume meat at 2+ meals per day. I collect and compile these, looking at the class average for trophic level. This info becomes valuable the next session, when we get into the issue that there are in-between cases (organisms that are not strictly primary consumer or secondary consumer), the difficulty of assigning a trophic level to an entire species given variation among individuals such as across developmental stages (omnivores as juvenile, vegetarian as adult), and also perhaps variation in ecological context (vegetarian on campus but omnivore at home), etc. We also talk about how data can be biased or inaccurate. What if people lied on the questionnaire? We then get into methods for validating trophic level estimates using multiple mechanisms, using analysis of nitrogen stable isotopes, or of stomach contents. This may be a little advanced, and not exactly hands-on, but it makes the topic relevant to their lives and the exercise is adaptable to other audiences and contexts. I find that almost everyone -- non-majors and majors alike -- likes to think about food, including how individual and human diets situate our species in the trophic pyramid, and the associated energetics.
