Mushrooms and other fungi seem to pop up after a period of rain, but this film clip makes it look instantaneous:
I found the film on the website, Fantastic Fungi: The Official Site for Everything Fungi. I guess in the 21st century you can expect fungi to have their own website, and blog, and Facebook page!
If you look at nothing else on the Fantastic Fungi website, make sure you look at the gallery of fungi photos. They are amazing!
I know that most people are hesitant about picking wild mushrooms, but there some in our area that are okay to eat. One is the Giant Puffball. I've seen a puffball the size of a basketball that was found in the woods in Windham. It smelled heavenly!
Backyard Foraging: 65 Familiar Plants You Didn't Know You Could Eat by Ellen Zachos [641.303 ZAC] has a chapter titled, "Friendly fungi: five easy mushrooms."