Radial Basis Function Networks are not talked about a lot these days, but they are very interesting and useful.
Handwriting demo: http://macheads101.com/demos/handwriting/?c=rbf
Resizing images with RBF networks: https://github.com/unixpickle/rbfscale#results
Distance formula in kNN video: https://youtu.be/2Al2Tyv_0EQ?t=435
Linear neurons: https://youtu.be/P02xWy63Q6U?t=378
Neural net training: https://www.youtube.com/watch?v=uHpKdZLutu0
Code to generate diagrams: https://gist.github.com/unixpickle/35404fb4aac196531b7ddfa97b764dcf