A new landing page now exists for apps that allow for the exploration of Landsat remotely sensed data that your students could use to examine geology, urban growth, water and water quality, and more, called "Unlock Earth's Secrets:"
I explain how to teach with this tool, here: New and Improved Landsat Apps
This web application highlights some of the capabilities for accessing Landsat imagery layers, powered by ArcGIS for Server, accessing Landsat Public Datasets running on the Amazon Web Services Cloud. The layers are updated with new Landsat images on a daily basis.
One of the new and improved Landsat images apps now available.