Number Theory:
Modular Arithmetic Calculator
Dario Alpern's number theory site
MathPages: Number Theory.

Knots:
The KnotPlot Site

Algebraic surfaces and singularities:
Herwig Hauser's singularities
Imaginary
AlgebraicSurface.net
Algebraic surface
4d animation

Fractals:
Wikipedia: Fractals
Fractal Zoom Mandelbrot Corner

Mathematical humour:
Collection of by Andrej and Elena Cherkaev
The komplex plane
The Math Humor Page
Foolproof: A Sampling of Mathematical Folk Humor
Wikipedia on Math Humour
More links at allmath.com
More links at EqWorld
More links at about.com

For math teachers:
JUMP Math

Other stuff:
Museum of Mathematics
The Power of Exponential Growth

Last update: May 23, 2023