How many kinds of foot fungus are there?

Technically...: if you mean KINDS as to type of species - it's quite numerous but the most common is trichophyton rubrum. Tinea pedis (aka foot fungus) is an infection which is the result of microscopic fungus organisms that lives on dead tissue of the hair and outer skin layers - TYPES include inter digitally, moccasin-like or vesicular. Onychomycosis describes fungal infection of the nails.

At least four.: There are at least 4 different organisms that cause fungal infection on the skin/nails of the feet. Most over the counter meds only kill one or two of them. T. rubrum and T. Mentagrophytes are 2 common ones.