The excitations in conventional superconductors, Bogoliubov quasiparticles, are spin-1/2 fermions but their charge is energy-dependent and, in fact, zero at the gap edge. Therefore, in superconductors (unlike normal metals) the spin and charge degrees of freedom may be separated. I shall review spin injection into conventional superconductors and focus on our recent experiments on mesoscopic superconductors. I will show how quasiparticle spin transport and out-of-equilibrium spin-dependent superconductivity can be triggered using the Zeeman splitting of the quasiparticle density of states in thin-film superconductors with small spin-mixing scattering. Finally, I will address the spin dynamics and the feedback of quasiparticle spin imbalances on the strength of the superconducting energy gap.