Wolfram
"The web's most extensive mathematics resource"
Mathematical Atlas
"A gateway to modern mathematics"
MacTutor Biografies
Biografies of famous mathematicians.
Theoretical Computer Science Cheat Sheet
Very handy. The author,
Dr. Steve Seiden, was run over by a truck and killed while riding his bike.
LATEX Cheat Sheet
Covers various output formats.
A Tutorial Introduction to the Lambda Calculus
Shows how to express basic arithmetic and propositional logic in Lambda Calculus.
Kiseido Go Server
Go equipment, information and the popular Kiseido Go Server.
The algebraic solution of an equation is no better than devising a symbol for the root of the equation and then saying that the equation has a root equal to the symbol.
(Gauss in his 1801 thesis)