A Few Discrete Mathematics Links

The Pi Search page
A history of the perfect number problem
A history of the perfect number problem with a list of those known
Biography of Paul Erdös
Biography of Georg Cantor
Biography of Leonhard Euler
A brief biography of Kurt Gödel
Biography of Johann Carl Friedrich Gauss
The Continuum Hypothesis
Euclid's Elements - David Joyce's applet version
The Happy End Problem
The Sierpinski Triangle
Derangements
Inclusion-Exclusion Principle
Introduction to Ramsey numbers
Graph crossing numbers
Birthday paradox

The MacTutor History of Mathematics archive

N is a Number A video biography of Paul Erdös

For further reading . . .

Proofs That Really Count
My Brain is Open: The Mathematical Journeys of Paul Erdös
Uncle Petros and Goldbach's Conjecture: A Novel of Mathematical Obsession
The Man Who Loved Only Numbers : The Story of Paul Erdös and the Search for Mathematical Truth
Fermat's Enigma: The Epic Quest to Solve the World's Greatest Mathematical Problem
Introduction to Graph Theory

Rules of cribbage