The number of unlabeled graphs
Stanisław Ulam
The Konigsberg bridge problem
William Rowan Hamilton
The Icosian game
Bob Bosch's Hamilton art
The Clay Millenium Problems
List of NP-complete problems
Guan Meigu
Residency matching
Math trades
Erdös numbers and collaboration distance
The Mathematics Geneology Project
The number of unlabeled tournaments
Maria Chudnovsky
The Strong Perfect Graph Theorem
György Hajós
Hugo Hadwiger
Planarity game
Stereographic projection video
Euler's Formula proofs
Platonic solids
The Appel and Haken proof of the Four Color Theorem part 1 and part 2
Appel and Haken printouts
The Robertson, Sanders, Seymour, Thomas proof of the Four Color Theorem and related files
The Gonthier proof of the Four Color Theorem