Provides updates on recent volcanic activity as well as geological history and information of volcanoes in the world for the last 10,000 years. It is an excellent resource for research papers needing geological history and accurate activity of volcanoes.
Sketchfab is a free 3D viewer that is extremely helpful during mineralogy. You are able to view a large variety of available minerals (Malachite, Selenite, etc) to identify specific structural features.
I mainly used slader for help with calculus homework but you can also search for textbook solutions to every subject.