General resources
Wikipedia,
Proof Wiki,
Citizendium,
NWE
AoPS wiki,
Math wiki,
nLab,
HyperMath,
PlanetMath
MIT Open Courseware
Knowino
Brilliant.org articles
Tricki
Math Stack Exchange
Few-subject resources
Math Proofs Jrensen
Eqworld
Human knowledge
Calculators and graphing
Desmos 2d graphing
Desmos 3d graphing
Other tools
OEIS
All LaTeX symbols list
Math genealogy
Floating point math
0.30000000000000004.com
Prime numbers
Prime wiki
Prime factorization visualization
GIMPS
The Prime Pages
Pending
Euler Map Theorem (V-E+F=2) Visual Proof
Wrath of Math: is everybody teaching this math wrong?
Trachtenberg system of multiplication
Math map (quanta magazine)
https://www.malinc.se/
https://youtube.com/playlist?list=PLUl4u3cNGP60hI9ATjSFgLZpbNJ7myAg6
https://retiredparkingguard.com/notes/mathematics/index.html
https://matthewfeickert.github.io/Statistics-Notes/introduction.html
PFD existence and uniqueness proof paper - proofs on why methods for partial fraction decomposition work and exist, as well as the existence and uniqueness of decompositions
https://youtube.com/playlist?list=PLZHQObOWTQDPD3MizzM2xVFitgF8hE_ab
https://youtube.com/playlist?list=PLZHQObOWTQDMsr9K-rj53DwVRMYO3t5Yr
https://youtube.com/playlist?list=PLZHQObOWTQDOMxJDswBaLu8xBMKxSTvg8
https://youtube.com/playlist?list=PLZHQObOWTQDNPOjrT6KVlfJuKtYTftqH6