Although many mathematicians are not particularly fond of football, and even more football fans and players are not very enthusiastic about maths, there are quite a few connections that give good examples for mathematicians and also many mathematical activities done by football fans and analysts on their own free will...
So far, the best text I found on this topic is John Wesson's book about physics and math in football. The title is "The Science of Soccer"; there is also a German translation "Fussball - Wissenschaft mit Kick". Besides this book, there are a few good links on the web:
On June 1st 2006. I held a talk at the Mathematical Colloquium at the Dept. of Mathematics in Osijek (Croatia) on this topic. Here is the corresponding power-point presentation. At the moment it is available only in Croatian, but I shall soon translate it to English.
Last update: Jun 28th, 2006.