Not long ago I happened across this nifty thing, a Back to the Roots Mushroom Kit. I didn't get any freebies from them - I saw the kit online, decided I'd take a chance and try it out. So far, it's pretty dang cool.
These guys take used coffee grounds from a local (to them) coffeeshop and prepare them for growing mushrooms. They ship you the kit, you soak it, you spritz it with water, and blammo: you get oyster mushrooms blasting out overnight.
If you are reading this and you happen to know my father, don't tell him about it. I want to give a kit to him for his next birthday. :)