The below websites are all good examples of ways to engage students beyond the actual Midway tour.
http://www.nationalgeographic.com/ - Notice on the bottom right there is an Educator's resource area. When you click on Classroom Resources, there are some great ways for teachers to expand classroom learning. But also, on that Classroom Resource page, there is a Kids link (on the left). Having different pages for teachers and students is a great way to expand learning beyond the tour.
http://www.si.edu/ Smithsonian also has sections (on the left) for teachers and students. Their educator section is so robust, with a seachable lesson plan bank. Remember when we discussed having teachers submit lessons? They could be part of this searchable database idea. They also have a neat "family" link, which pulls in the entire community of learners.
The Field Museum in Chicago has a great section for virtual experiences: http://www.fieldmuseum.org/education/online_learn.htm Again, a great way to extend the learning beyond the 45 minutes, or 2 hours. Teachers can use these as pre or post activities.
Someone mentioned, I think, Discovery Education. Although the site has a ton of resources (http://school.discoveryeducation.com/) I dont think the site is a good model for what the Midway is trying to create. It's a plethora of activities, worksheets, and interactive elements. But maybe it would make for a good partner to be able to pull some of their resources, or joint-development of projects down the road.
When we talk about how to present topics via online learning, it needs to be simple because there may be teachers who aren't real confident in the topic. We have some teachers who use lessons similar to this one: http://www.thetech.org/exhibits/online/topics/12a.html It's a lot of text, yes, but it has some graphical interface and helps the teacher present the information to the class, even if they aren't a subject-matter expert.
Did I promise to share anything else? I can't recall. Just let me know.
Laura