MADD Quiz:
https://canvas.uchicago.edu/courses/18131/quizzes/66863
TinkerCAD:
https://www.tinkercad.com/
Thingiverse (find 3D models):
https://www.thingiverse.com/
2D images to STL (3D):
https://www.3dforprint.com/image-to-stl/