Math links:

Introduction to differential forms playlist: https://www.youtube.com/playlist?list=PLB8F2D70E034E9C29
Classical differential geometry notes: http://liavas.net/courses/math430/

Topology Lectures by Dr Tadashi Tokieda: https://www.youtube.com/watch?v=SXHHvoaSctc&list=PLTBqohhFNBE_09L0ilf3fYXF5woAbrzJ
Snoopy Topology Notes (written by a class of students): https://www.math.colostate.edu/~renzo/teaching/Topology10/Notes.pdf

Quick and Dirty Introduction to Exterior Calculus has gone offline, but archived notes are on Wayback Machine:
https://web.archive.org/web/20191221153300/http://brickisland.net/cs177/?p=174
https://web.archive.org/web/20191221153400/http://brickisland.net/cs177/?p=184
https://web.archive.org/web/20191221195625/http://brickisland.net/cs177/?p=200
https://web.archive.org/web/20191222002003/http://brickisland.net/cs177/?p=248
https://web.archive.org/web/20191221104907/http://brickisland.net/cs177/?p=264