How to Gamble If You Must
Well written, quite enjoyable.
http://www.maa.org/sites/default/files/pdf/joma/Volume8/Siegrist/RedBlack.pdf
see also http://www.math.uah.edu/stat/
http://www.maa.org/sites/default/files/pdf/joma/Volume8/Siegrist/RedBlack.pdf
see also http://www.math.uah.edu/stat/