If you've not been following along on the GIS Education Community blog be sure to check out George Dailey's series covering National Parks and ArcGIS Explorer. The 10-part post was inspired by the PBS special The National Parks: America's Best Idea and not only provides a great tour of parks, but also demonstrates how the unique capabilities of ArcGIS Explorer can be leveraged to do some really interesting things. Part 10 was recently published, and here's a handy reference to all of the posts.