I'm looking for free / open source GIS education sources for advanced GIS users. Specifically sources that cover programming, spatial analysis, modeling, spatial databases / data management. I use mostly ArcGIS as a federal employee, but sources that go into conceptual concepts are appreciated too.
I'm a big fan of the Penn State Masters in GIS program because they offer many of their full classes under the MIT license. I'm also reading through the lectures from the Dublin Institute of Technology. I'm hoping that there are other high quality resources out there that I haven't come across yet.
While I would prefer actual courses that have some degree of interactiveness (like quizes or tasks associated with lessons), books should be considered if they are high-quality, free resources.