This slime mold has some pretty unsavory names, like dog vomit, but it is commonplace in damp weather, on rotting leaves, wood and in bark mulch. It munches on fungal spores, bacteria, and other microbes. Slime mold is pretty amazing stuff. It is a “eukaryotic microbe”—a giant, single-celled organism, one of more than 30,000 species. And it’s smart:
A team of Japanese and Hungarian researchers, writing in the journal Nature, claimed to have found the slime mold Physarum polycephalum is capable of finding the shortest way through a maze. Pieces of the slime mould were enticed through a 30-square-centimetre (five-square-inch) maze by the prospect of food at the end of the puzzle. The researchers concluded that the creature was exhibiting a kind of primitive intelligence.
Normally, the slime spreads out its network of tube-like legs, or pseudopodia, to fill all the available space. But when two pieces of food were placed at separate exit points in the labyrinth, the organism squeezed its entire body between the two nutrients. It adopted the shortest possible route, effectively solving the puzzle. 
So why not put it to work? Say, by designing a mass transport system, as these researchers from the University of Oxford did.
Identification: The bright yellow, jellylike slime, which seems to appear out of nowhere after wet weather, is conspicuous and hard to confuse. Photo 16 shows it in a hard, crusty phase, with a white powdery top. In photo 8, it is in its dormant, dried out phase. This looks a bit like soil, but it is a fine powder which explodes like a smoke bomb if you step on it.
Edibility: Just kidding.
I took a time lapse movie of this slime mold, atop some decaying bark mulch. It appeared to be dormant for most of the several hours, but in this segment, covering about 15-20 minutes, it seems to come alive like a creature from the Twilight Zone:
(Or see it larger here .)
Physarum polycephalum on Wikipedia
Physarum polycephalum at Utah State University’s Fun Facts About Fungi
Physarum polycephalum on www.fnanaturesearch.org
Physarum polycephalum on Stephen Sharnoff Photography
Physarum polycephalum on Discover Life
Physarum polycephalum on www.buildingthepride.com (grow your own!)
Physarum polycephalum description by Thomas H. Kent, last updated 16 Aug 2013.