I run the site mathpuzzle, and used to be the main advisor for the TV show Numb3rs. I've contributed extensively to MathWorld. Before that, I wrote the Math Games columns for the MAA. I am now the chief editor for the Wolfram Demonstrations Project. Of my own Demonstrations there, some of my favorites are: - Mrs. Perkins's Quilts - Tightly Packed Squares - Social Golfer Problem - The Circles Of Descartes - Triangle Calculator