You never know where you'll find something fun and useful. We're slowly and not always steadily working our way through third grade chemistry this year, when lo and behold what do I find Heidi doing over at 101 Cookbooks?
Making Liquid Nitrogen Ice Cream! Heidi not only provides a delicious-sounding gelato-type base for the experiment (check the comments for the recipe specifics), but also some great links for food science and molecular gastronomy.
101 Cookbooks is a terrific blog, whether you're interested in reading about food or cookbooks, actually cooking, or doing some science. Highly recommended.