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