Cryo EM:
https://em-learning.com/ – video series by Grant Jensen
https://www2.mrc-lmb.cam.ac.uk/research/scientific-training/electron-microscopy/ – video series MRC Laboratory of Molecular Biology
General EM sample preperation:
https://www.leica-microsystems.com/products/sample-preparation-for-electron-microscopy/ – lots of different sample preperation methods with LEICA Instruments
Transmission EM:
http://www.rodenburg.org/ – learn TEM/STEM alignment
Youtube channel mostly dedicated to STEM with some useful tutorials:
https://www.youtube.com/channel/UCejMCxv5psUKJTrdL2-ZjmQ
Atumtome:
https://www.youtube.com/watch?v=vSImAY1rSFE
An introduction to On-section CLEM: