I didn't notice anyone referring to dofmaster.com. There one will find a very instructional software package that is Windows friendly, and which has tunable parameters for focal lengths, formats, circles of confusion, etc. The program puts a DOF calculator on the screen, sort of a circular slide rule. It can be changed, operated, and even printed out to make a field serviceable DOF calculator. This may be of interest to people who have cameras without DOF indications, or to students who want to understand DOF better.
There is also a Palm Pilot variant on the same website. It is all available via FREE downloads.