I recently attended a terrific workshop about mushroom gardening, held at the Berkeley Eco-House. We spent the day propagating edible mushrooms using bags of sanitized straw, oak logs, and saw dust as the growing mediums, and mushroom spawn carried by dowel rods and saw dust as the "seeds" for the project. I now have several bags of straw filled with mushroom spawn and a "plugged log" to add to my garden's edible offerings. In 6-8 weeks, I should have my first mushroom harvest if all goes well! It will be nice to have oyster mushrooms, nameko mushrooms, lion's mane mushrooms and more in the garden. Stay tuned.
One great source for mushroom growing kits and starter spawn for edible mushrooms is Fungi Perfecti: http://www.fungi.com/ Their work and their products are great. I also enjoyed reading Paul Stamets's book titled, Mycelium Running. The level of detail is excellent and the in-depth examples are very interesting.
I also plan to try some of Fungi Perfecti's mycorrhizal fungi products in my garden this year. These products contain mushroom spores from beneficial fungi species that attach to plant roots and help them to gather nutrients from the soil--producing larger crops and healthier plants. See http://www.fungi.com/mycogrow/index.html for more information.