  We introduce a functorial construction which, from a monoid, produces a
set-operad. We obtain new (symmetric or not) operads as suboperads or quotients
of the operad obtained from the additive monoid. These involve various familiar
combinatorial objects: parking functions, packed words, planar rooted trees,
generalized Dyck paths, Schr\"oder trees, Motzkin paths, integer compositions,
directed animals, etc. We also retrieve some known operads: the magmatic
operad, the commutative associative operad, and the diassociative operad.
