  We investigate observable cosmological aspects of sterile neutrino dark
matter produced via the freeze-in mechanism. The study is performed in a
framework that admits many cosmologically interesting variations: high
temperature production via annihilation processes from higher dimensional
operators or low temperature production from decays of a scalar, with the
decaying scalar in or out of equilibrium with the thermal bath, in
supersymmetric or non-supersymmetric setups, thus allowing us to both extract
generic properties and highlight features unique to particular variations. We
find that while such sterile neutrinos are generally compatible with all
cosmological constraints, interesting scenarios can arise where dark matter is
cold, warm, or hot, has nontrivial momentum distributions, or provides
contributions to the effective number of relativistic degrees of freedom Neff
during Big Bang nucleosynthesis large enough to be probed by future
measurements.
