American Scientist: Mathematics [the Mathematics section of a general interest science magazine]
Euclid’s Elements, Books 1-6 (of 13) [texts and diagrams from Euclid’s seminal work on geometry]
Geometrical Solutions Derived from Mechanics: a treatise of Archimedes [texts and diagrams from Archimedes’ influential ancient geometry]
The Golden Ratio [a short video explicating one of the most beautiful and influential patterns uncovered by geometry]
Rene Descartes’ La Geometrie (in French) [the text of Descartes’ groundbreaking work of modern geometry]
Math is Fun [a website for Mathematics with materials for all ages]
Nautilus: Mathematics [the Mathematics section of a general interest Science magazine]
Quanta [the website for a magazine about mathematics, physics, biology, and computer science]
Story of Mathematics [a resource for the history of Mathematics in a wide range of cultures]
Wolfram MathWorld [an encyclopedia for virtually all areas of Mathematics]