Snail Power is a prealgebra mathematics lesson about proportional reasoning and making mathematical comparisons. In the lesson, students collect data about the pulling strength of a land snail by (humanely) connecting it to a pulling harness. We then compare the strength data for the various snails, and discover how much we humans could pull if we were, relatively speaking, as strong as a snail.
In all fairness, there's a lot of overhead to this lesson. Working with live animals -- and caring for them in the "off season" -- requires ongoing attention that will make this lesson prohibitive for most teachers. Plus, there are probably hundreds of activities that could teach the same mathematical content.
However... I have never taught a lesson that brings more delight and energy to my classroom. This lesson is a show-stopper that students will remember and talk about for years!
Here's a link to a shared folder that contains both the conference presentation slides and the student-facing presentation.
For those who would like to learn more about keeping snails as classroom pets, I recommend the websites www.petsnails.co.uk and www.molluscs.at.