Free lecture notes, exams, and other resources from MIT courses. Use the search box to find courses that might not be obvious at first (e.g., search "geographic" to find courses using GIS, some in Civil Engineering)
Browse ArcGIS online content such as maps and applications published by Esri and the user community. Many of the maps are freely available and you can use them directly in your desktop or Web applications. You can also upload your own content and share it with the user community.