Sheila B's Popcorn Factory gave a great tour for our little homeschooling group. The factory is actually just a small building off the highway in even smaller, Manson, Iowa. I arranged a tour with the owner a week or two in advance. When we first arrived we had a brief orientation about the factory in the lobby, where the owner explained a little about their company, such as who they supply, and where they get their wrappers. He also explained that his now deceased wife's name was Sheila B., for whom he named the company.
The tour lasted about an hour long total, I guess...and was pretty interesting. The owner walked us through the entire process, from putting the butter into the bags, to folding and wrapping, to packaging. Nothing was left out. The owner was very proud of his company and really seemed to enjoy giving us the tour. (I've been on two here and both times he was just as pleasant as could be.)
At the end of the tour each kid got their own bag of microwave popping corn, and a little education on How's That Made?