Nonlinear optics at nanoscale is a recent fascinating research field. Among the numerous nonlinear optics phenomena, stimulated Raman scattering is one of the most interestingphenomena, due to its significant implications from both fundamental and applicative point of view. In this paper, the observations of stimulated Raman scattering, at the wavelengths of interest for telecommunications, in silicon nanocomposite and in amorphous silicon nanoparticles are reported. A significant Raman gain enhancement and a significant threshold power reduction with respect to silicon are demonstrated. Our findings indicate that nanostructured materials show great promise for Si-based Raman lasers.