So there you have it --- several cheap or free techniques to reproduce your edible mushrooms.  I'll keep you posted on how our various experiments go, but I'd also love to hear from some of you who try these (or other) techniques.

As a final note, Paul Stamets warns that different species of mushrooms respond better to different techniques.  It sounds like it's hard to go wrong with creating new logs of oyster mushrooms, but shiitakes might take a bit more trial and error.  The book notes that shiitake spores must be dried and then rehydrated in order to grow and shiitakes aren't listed as good candidates for stem butt reproduction.  Sounds like a good challenge!