  We generalize a recently proposed mechanism for the origin of primordial
metric perturbations in inflationary models. Quantum fluctuations of light
scalar fields during inflation give rise to super-horizon fluctuations of
masses and reaction rates of various particles. Reheating, freeze-out, and
matter-domination processes become inhomogeneous and generate super-horizon
metric perturbations. We also calculate the degree of non-Gaussianity $f_{nl}$
for this new model of cosmological perturbations. The precise value of $f_{nl}$
depends on the specific models, but $|f_{nl}|\sim$few is a natural lower bound
for our mechanisms. This is much larger than the currently assumed theoretical
value $f_{nl}\sim tilt \lesssim 0.05$, and is thought to be observable. In a
particularly attractive model of inhomogeneous mass-domination, the
non-Gaussianity of perturbations generated by our mechanism is simply
$f_{nl}=5$, irrespective of the detailed structure of the underlying field
theory.
