This excellent thing appeared overnight in the front yard. It appears to be Fuligo septica, which rather unfairly I think goes by the popular name dog vomit slime mold. The resemblance is there, but there aren't many dogs that could produce such a color, unless they had snuck into the turmeric. At any rate, the slime mold is a fascinating and often beautiful organism.
I include an additional photo for those whose tastes in flora run in a more conventional direction: one of several glorious ceanothus bushes in the back yard. A native plant every drought-conscious California gardener should consider: looks fantastic year round, and thrives on neglect.