There is so much variation in making a duct tape wallet that I am posting more than one tutorial. Huge thanks to Richard Portune for making an impressive (if somewhat daunting) tutorial for a bifold.
A fairly complicated bifold wallet - Tutorial written by Richard Portune
simple wallet - Tutorial written by Samuel Peck
Dustin Kirk's tutorial - external link found by Kenneth Finnegan
Make Magazine tutorial - PDF tutorial by Make Magazine on how to make a simple duct tape wallet - external link found by Kenneth Finnegan