uwusearch

supersearches: [logic]
sidesearches: physics, philosophy
subsearches: [arithmetic], [elementary (high school/college) algebra], [calculus],
         [linear algebra], [real analysis], [abstract algebra],


General resources
Wikipedia, Wolfram mathworld, Citizendium, NWE
AoPS wiki, Math wiki, nLab, HyperMath, PlanetMath
MIT Open Courseware
Khan Academy, Knowino

Proof Wiki
Brilliant.org articles
Tricki - Math problem solving techniques wiki

Math Stack Exchange - Math Q&A website

Few-subject resources
3Blue1Brown
Math Proofs Jrensen

Eqworld - differential, integral and functional equation exact solutions
Human knowledge

Calculators
Desmos 3d graphing
Wolfram Alpha

Other tools
OEIS - Integer sequences lookup
Detexify, All LaTeX symbols list - Find LaTeX symbols tools
Math genealogy

Floating point math
0.30000000000000004.com

Prime numbers
Prime wiki
Prime factorization visualization
GIMPS - Lend your computer to help find (mersenne) primes
t5k.org

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)