A large collection of cryptarithms and alphametics, including cryptarithms from the journal Sphinx, a Primer on Cryptarithmetic, books, and links to other collections of alphametics on the Web.

Include news, math tricks, methods, facts, trivia, mostly posted by users.

Visual animations of famous curves.

Individual pages on different topics in Mathematics. Examples : group theory, dynamical systems theory, geometry or number theory.

Topics include Flexagon, Soma Cube, Pentominos, Cube-it, Rubik's Cube, Froebel's Star, Tangram, House of Santa Claus, Chronogram, Numeric Palindromes, Latticework of Letters. English/German.

Includes puzzles, jokes, quotations, poetry, and FAQs.

Features interesting facts about different numbers. Includes favorite related links.

Home of Simon Singh: author, journalist and TV producer, specialising in science and mathematics. Cryptography is one of his specialties, and his site has a lot of educational and fun content about codes and codebreaking.