Terbinafine (Lamisil) is the most effective compound against that: http://en.wikipedia.org/wiki/T...
1 week of exposure is enough to eradicate all traces of the fungi that cause athlete's foot. Lamisil Once is very effective if you're lazy or forgetful.
If you prefer 'natural' methods, you can apply (or soak in) a sufficiently acidic solution of citric acid or vinegar for two weeks. Skip a day and the two-week counter resets, as the method relies on the fungi not reproducing until they all die naturally. The same goes for most anti-fungal treatments, by the way (which is why Lamisil Once is so effective).
While we're on the subject of fungi: dandruff is often caused by the fungus http://en.wikipedia.org/wiki/M... (globosa), which feeds on the lipids on your scalp.
http://en.wikipedia.org/wiki/Z... is quite effective in dealing with the fuckers, without requiring a prescription from your doctor.